diff --git a/languages/jetbrains.mps.lang.typesystem2/sandbox/jetbrains.mps.lang.typesystem2.samplechecker.handler.util/models/jetbrains/mps/lang/typesystem2/samplechecker/handle/util.mps b/languages/jetbrains.mps.lang.typesystem2/sandbox/jetbrains.mps.lang.typesystem2.samplechecker.handler.util/models/jetbrains/mps/lang/typesystem2/samplechecker/handle/util.mps
index 356f199c..a572b312 100644
--- a/languages/jetbrains.mps.lang.typesystem2/sandbox/jetbrains.mps.lang.typesystem2.samplechecker.handler.util/models/jetbrains/mps/lang/typesystem2/samplechecker/handle/util.mps
+++ b/languages/jetbrains.mps.lang.typesystem2/sandbox/jetbrains.mps.lang.typesystem2.samplechecker.handler.util/models/jetbrains/mps/lang/typesystem2/samplechecker/handle/util.mps
@@ -342,9 +342,9 @@
         <node concept="3clFbH" id="3KV3FXjZHi6" role="3cqZAp" />
         <node concept="3cpWs8" id="5uFPQ7ClQgq" role="3cqZAp">
           <node concept="3cpWsn" id="5uFPQ7ClQgr" role="3cpWs9">
-            <property role="TrG5h" value="computingSession" />
+            <property role="TrG5h" value="sessionSolver" />
             <node concept="3uibUv" id="5uFPQ7ClQgn" role="1tU5fm">
-              <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="ComputingSession" />
+              <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="SessionSolver" />
             </node>
             <node concept="2OqwBi" id="5uFPQ7ClQgs" role="33vP2m">
               <node concept="2YIFZM" id="5uFPQ7ClQgt" role="2Oq$k0">
@@ -371,7 +371,7 @@
                 <node concept="1pGfFk" id="3KV3FXk0plg" role="2ShVmc">
                   <ref role="37wK5l" node="3KV3FXjZFyb" resolve="LubSolver" />
                   <node concept="37vLTw" id="3KV3FXk0r_h" role="37wK5m">
-                    <ref role="3cqZAo" node="5uFPQ7ClQgr" resolve="computingSession" />
+                    <ref role="3cqZAo" node="5uFPQ7ClQgr" resolve="sessionSolver" />
                   </node>
                 </node>
               </node>
@@ -418,12 +418,12 @@
               <node concept="3clFbF" id="3KV3FXjZMUG" role="3cqZAp">
                 <node concept="2OqwBi" id="3KV3FXjZMUH" role="3clFbG">
                   <node concept="37vLTw" id="3KV3FXk0rYO" role="2Oq$k0">
-                    <ref role="3cqZAo" node="5uFPQ7ClQgr" resolve="computingSession" />
+                    <ref role="3cqZAo" node="5uFPQ7ClQgr" resolve="sessionSolver" />
                   </node>
                   <node concept="liA8E" id="3KV3FXjZMUJ" role="2OqNvi">
                     <ref role="37wK5l" to="qrld:4xBopTznPKO" resolve="tell" />
                     <node concept="10M0yZ" id="3KV3FXjZMUK" role="37wK5m">
-                      <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
+                      <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
                       <ref role="3cqZAo" to="oy3s:5uFPQ7C23RV" resolve="EQ_SYM" />
                     </node>
                     <node concept="37vLTw" id="3KV3FXjZMUL" role="37wK5m">
@@ -1478,7 +1478,7 @@
       <node concept="37vLTG" id="3KV3FXjZFT2" role="3clF46">
         <property role="TrG5h" value="computingSession" />
         <node concept="3uibUv" id="3KV3FXjZFTc" role="1tU5fm">
-          <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="ComputingSession" />
+          <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="SessionSolver" />
         </node>
       </node>
       <node concept="3cqZAl" id="3KV3FXjZFyd" role="3clF45" />
@@ -1738,7 +1738,7 @@
           <node concept="3cpWsn" id="5uFPQ7ClVCK" role="3cpWs9">
             <property role="TrG5h" value="computingSession" />
             <node concept="3uibUv" id="5uFPQ7ClVCL" role="1tU5fm">
-              <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="ComputingSession" />
+              <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="SessionSolver" />
             </node>
             <node concept="2OqwBi" id="5uFPQ7ClVCM" role="33vP2m">
               <node concept="2YIFZM" id="5uFPQ7ClVCN" role="2Oq$k0">
@@ -1826,7 +1826,7 @@
                   <node concept="liA8E" id="3KV3FXk1m3b" role="2OqNvi">
                     <ref role="37wK5l" to="qrld:4xBopTznPKO" resolve="tell" />
                     <node concept="10M0yZ" id="3KV3FXk1m3c" role="37wK5m">
-                      <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
+                      <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
                       <ref role="3cqZAo" to="oy3s:5uFPQ7C23RV" resolve="EQ_SYM" />
                     </node>
                     <node concept="37vLTw" id="3KV3FXk1m3d" role="37wK5m">
@@ -2349,7 +2349,7 @@
       <node concept="37vLTG" id="3KV3FXk1jlA" role="3clF46">
         <property role="TrG5h" value="computingSession" />
         <node concept="3uibUv" id="3KV3FXk1jl_" role="1tU5fm">
-          <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="ComputingSession" />
+          <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="SessionSolver" />
         </node>
       </node>
     </node>
@@ -2541,12 +2541,12 @@
         <node concept="3cpWs6" id="3KV3FXjZkQU" role="3cqZAp">
           <node concept="2OqwBi" id="3KV3FXjZkQV" role="3cqZAk">
             <node concept="37vLTw" id="3KV3FXjZkRN" role="2Oq$k0">
-              <ref role="3cqZAo" node="3KV3FXjZFTt" resolve="computingSession" />
+              <ref role="3cqZAo" node="3KV3FXjZFTt" resolve="sessionSolver" />
             </node>
             <node concept="liA8E" id="3KV3FXjZkQX" role="2OqNvi">
               <ref role="37wK5l" to="qrld:4xBopTznHV5" resolve="ask" />
               <node concept="10M0yZ" id="5uFPQ7C5ZbN" role="37wK5m">
-                <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                 <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
               </node>
               <node concept="37vLTw" id="3KV3FXjZkRO" role="37wK5m">
@@ -2643,30 +2643,30 @@
         <node concept="3clFbF" id="3KV3FXk1u66" role="3cqZAp">
           <node concept="37vLTI" id="3KV3FXk1uaA" role="3clFbG">
             <node concept="37vLTw" id="3KV3FXk1ubz" role="37vLTx">
-              <ref role="3cqZAo" node="3KV3FXk1u5_" resolve="computingSession" />
+              <ref role="3cqZAo" node="3KV3FXk1u5_" resolve="sessionSolver" />
             </node>
             <node concept="2OqwBi" id="3KV3FXk1u6y" role="37vLTJ">
               <node concept="Xjq3P" id="3KV3FXk1u65" role="2Oq$k0" />
               <node concept="2OwXpG" id="3KV3FXk1u8T" role="2OqNvi">
-                <ref role="2Oxat5" node="3KV3FXjZFTt" resolve="computingSession" />
+                <ref role="2Oxat5" node="3KV3FXjZFTt" resolve="sessionSolver" />
               </node>
             </node>
           </node>
         </node>
       </node>
       <node concept="37vLTG" id="3KV3FXk1u5_" role="3clF46">
-        <property role="TrG5h" value="computingSession" />
+        <property role="TrG5h" value="sessionSolver" />
         <node concept="3uibUv" id="3KV3FXk1u5$" role="1tU5fm">
-          <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="ComputingSession" />
+          <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="SessionSolver" />
         </node>
       </node>
     </node>
     <node concept="2tJIrI" id="3KV3FXk1qx0" role="jymVt" />
     <node concept="312cEg" id="3KV3FXjZFTt" role="jymVt">
-      <property role="TrG5h" value="computingSession" />
+      <property role="TrG5h" value="sessionSolver" />
       <node concept="3Tmbuc" id="3KV3FXk1ru9" role="1B3o_S" />
       <node concept="3uibUv" id="3KV3FXjZFTw" role="1tU5fm">
-        <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="ComputingSession" />
+        <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="SessionSolver" />
       </node>
     </node>
   </node>
diff --git a/languages/jetbrains.mps.lang.typesystem2/sandbox/jetbrains.mps.lang.typesystem2.sampleplugin/models/jetbrains/mps/lang/typesystem2/sampleplugin/plugin.mps b/languages/jetbrains.mps.lang.typesystem2/sandbox/jetbrains.mps.lang.typesystem2.sampleplugin/models/jetbrains/mps/lang/typesystem2/sampleplugin/plugin.mps
index 38825fdc..927c182e 100644
--- a/languages/jetbrains.mps.lang.typesystem2/sandbox/jetbrains.mps.lang.typesystem2.sampleplugin/models/jetbrains/mps/lang/typesystem2/sampleplugin/plugin.mps
+++ b/languages/jetbrains.mps.lang.typesystem2/sandbox/jetbrains.mps.lang.typesystem2.sampleplugin/models/jetbrains/mps/lang/typesystem2/sampleplugin/plugin.mps
@@ -1729,22 +1729,22 @@
         <node concept="3g6Rrh" id="5mr7UHcboy8" role="2ShVmc">
           <node concept="10M0yZ" id="5mr7UHcboyR" role="3g7hyw">
             <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
-            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
           </node>
           <node concept="10M0yZ" id="5mr7UHcboyX" role="3g7hyw">
             <ref role="3cqZAo" to="oy3s:5uFPQ7C23RV" resolve="EQ_SYM" />
-            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
           </node>
           <node concept="10M0yZ" id="5mr7UHcboz3" role="3g7hyw">
-            <ref role="1PxDUh" to="oy3s:6infEALAfer" resolve="AssertBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:6infEALAfer" resolve="AssertPredicate" />
             <ref role="3cqZAo" to="oy3s:5uFPQ7BZnLB" resolve="ASSERT_SYM" />
           </node>
           <node concept="10M0yZ" id="5mr7UHcboz9" role="3g7hyw">
-            <ref role="1PxDUh" to="xq5w:5$WbtTOYoMb" resolve="LogicalBuiltinConstraint" />
+            <ref role="1PxDUh" to="xq5w:5$WbtTOYoMb" resolve="LogicalPredicate" />
             <ref role="3cqZAo" to="xq5w:5uFPQ7C26$b" resolve="BOUND_SYM" />
           </node>
           <node concept="10M0yZ" id="5mr7UHcbozf" role="3g7hyw">
-            <ref role="1PxDUh" to="xq5w:5$WbtTOYoMb" resolve="LogicalBuiltinConstraint" />
+            <ref role="1PxDUh" to="xq5w:5$WbtTOYoMb" resolve="LogicalPredicate" />
             <ref role="3cqZAo" to="xq5w:5uFPQ7C279$" resolve="FREE_SYM" />
           </node>
           <node concept="3uibUv" id="5mr7UHcbqo2" role="3g7fb8">
@@ -5822,6 +5822,11 @@
                                   <ref role="3cqZAo" node="78CwJJcTyWt" resolve="nameHint" />
                                 </node>
                               </node>
+                              <node concept="2ShNRf" id="2tcGHBEvatL" role="37wK5m">
+                                <node concept="HV5vD" id="2tcGHBEvatM" role="2ShVmc">
+                                  <ref role="HV5vE" to="95zw:7ISVfSIxNO" resolve="JchrSolver" />
+                                </node>
+                              </node>
                             </node>
                           </node>
                         </node>
diff --git a/languages/jetbrains.mps.logic/jchr/models/jetbrains/mps/logic/jchr/predicate.mps b/languages/jetbrains.mps.logic/jchr/models/jetbrains/mps/logic/jchr/predicate.mps
index b271ace0..fc85b437 100644
--- a/languages/jetbrains.mps.logic/jchr/models/jetbrains/mps/logic/jchr/predicate.mps
+++ b/languages/jetbrains.mps.logic/jchr/models/jetbrains/mps/logic/jchr/predicate.mps
@@ -19,6 +19,7 @@
     <import index="yg8f" ref="r:e213377a-f1a7-4ba7-9d08-96bcb97ed8ce(jetbrains.mps.logic.builtin)" />
     <import index="33ny" ref="6354ebe7-c22a-4a0f-ac54-50b52ab9b065/java:java.util(JDK/)" />
     <import index="xq5w" ref="r:729bada4-05fa-458f-8bf8-28b9cb978726(jetbrains.mps.logic.builtin.var)" />
+    <import index="e2ud" ref="r:86a12676-9e8d-407a-83b6-a911ff5a7cf8(jetbrains.mps.logic.builtin.java)" />
   </imports>
   <registry>
     <language id="f3061a53-9226-4cc5-a443-f952ceaf5816" name="jetbrains.mps.baseLanguage">
@@ -195,6 +196,9 @@
         <child id="5375687026011219971" name="member" index="jymVt" unordered="true" />
       </concept>
       <concept id="1171903607971" name="jetbrains.mps.baseLanguage.structure.WildCardType" flags="in" index="3qTvmN" />
+      <concept id="1171903916106" name="jetbrains.mps.baseLanguage.structure.UpperBoundType" flags="in" index="3qUE_q">
+        <child id="1171903916107" name="bound" index="3qUE_r" />
+      </concept>
       <concept id="7812454656619025416" name="jetbrains.mps.baseLanguage.structure.MethodDeclaration" flags="ng" index="1rXfSm">
         <property id="8355037393041754995" name="isNative" index="2aFKle" />
       </concept>
@@ -237,6 +241,9 @@
       <concept id="1146644602865" name="jetbrains.mps.baseLanguage.structure.PublicVisibility" flags="nn" index="3Tm1VV" />
       <concept id="1146644623116" name="jetbrains.mps.baseLanguage.structure.PrivateVisibility" flags="nn" index="3Tm6S6" />
       <concept id="1146644641414" name="jetbrains.mps.baseLanguage.structure.ProtectedVisibility" flags="nn" index="3Tmbuc" />
+      <concept id="1116615150612" name="jetbrains.mps.baseLanguage.structure.ClassifierClassExpression" flags="nn" index="3VsKOn">
+        <reference id="1116615189566" name="classifier" index="3VsUkX" />
+      </concept>
       <concept id="1178893518978" name="jetbrains.mps.baseLanguage.structure.ThisConstructorInvocation" flags="nn" index="1VxSAg" />
       <concept id="1080120340718" name="jetbrains.mps.baseLanguage.structure.AndExpression" flags="nn" index="1Wc70l" />
     </language>
@@ -271,7 +278,7 @@
         <node concept="2B6LJw" id="6infEALAbJg" role="2B76xF">
           <ref role="2B6OnR" to="f8dg:~JCHR_Tells.value()" resolve="value" />
           <node concept="10M0yZ" id="6infEALACqu" role="2B70Vg">
-            <ref role="1PxDUh" to="oy3s:6infEALAfer" resolve="AssertBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:6infEALAfer" resolve="AssertPredicate" />
             <ref role="3cqZAo" to="oy3s:6infEALAgS7" resolve="ASSERT" />
           </node>
         </node>
@@ -298,7 +305,7 @@
         <node concept="2B6LJw" id="6infEALADHN" role="2B76xF">
           <ref role="2B6OnR" to="f8dg:~JCHR_Tells.value()" resolve="value" />
           <node concept="10M0yZ" id="6infEALADHO" role="2B70Vg">
-            <ref role="1PxDUh" to="oy3s:6infEALAfer" resolve="AssertBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:6infEALAfer" resolve="AssertPredicate" />
             <ref role="3cqZAo" to="oy3s:6infEALAgS7" resolve="ASSERT" />
           </node>
         </node>
@@ -322,7 +329,7 @@
         <node concept="2B6LJw" id="6infEALAc0z" role="2B76xF">
           <ref role="2B6OnR" to="f8dg:~JCHR_Asks.value()" resolve="value" />
           <node concept="10M0yZ" id="6infEALACVN" role="2B70Vg">
-            <ref role="1PxDUh" to="oy3s:6infEALAfer" resolve="AssertBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:6infEALAfer" resolve="AssertPredicate" />
             <ref role="3cqZAo" to="oy3s:6infEALAgS7" resolve="ASSERT" />
           </node>
         </node>
@@ -349,7 +356,7 @@
         <node concept="2B6LJw" id="6infEALAFgU" role="2B76xF">
           <ref role="2B6OnR" to="f8dg:~JCHR_Asks.value()" resolve="value" />
           <node concept="10M0yZ" id="6infEALAFgV" role="2B70Vg">
-            <ref role="1PxDUh" to="oy3s:6infEALAfer" resolve="AssertBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:6infEALAfer" resolve="AssertPredicate" />
             <ref role="3cqZAo" to="oy3s:6infEALAgS7" resolve="ASSERT" />
           </node>
         </node>
@@ -367,7 +374,7 @@
             <node concept="2B6LJw" id="6infEALAaAW" role="2B76xF">
               <ref role="2B6OnR" to="f8dg:~JCHR_Constraint.identifier()" resolve="identifier" />
               <node concept="10M0yZ" id="6infEALAaAX" role="2B70Vg">
-                <ref role="1PxDUh" to="oy3s:6infEALAfer" resolve="AssertBuiltinConstraint" />
+                <ref role="1PxDUh" to="oy3s:6infEALAfer" resolve="AssertPredicate" />
                 <ref role="3cqZAo" to="oy3s:6infEALAgS7" resolve="ASSERT" />
               </node>
             </node>
@@ -570,6 +577,7 @@
         </node>
       </node>
     </node>
+    <node concept="2tJIrI" id="2tcGHBEqirK" role="jymVt" />
     <node concept="2tJIrI" id="4xBopTzrSfF" role="jymVt" />
     <node concept="3clFb_" id="4xBopTzrRGH" role="jymVt">
       <property role="1EzhhJ" value="false" />
@@ -727,7 +735,7 @@
         <node concept="2B6LJw" id="6infEALAKQE" role="2B76xF">
           <ref role="2B6OnR" to="f8dg:~JCHR_Tells.value()" resolve="value" />
           <node concept="10M0yZ" id="6infEALAKQF" role="2B70Vg">
-            <ref role="1PxDUh" to="oy3s:6infEALAfer" resolve="AssertBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:6infEALAfer" resolve="AssertPredicate" />
             <ref role="3cqZAo" to="oy3s:6infEALAgS7" resolve="ASSERT" />
           </node>
         </node>
@@ -777,7 +785,7 @@
         <node concept="2B6LJw" id="6infEALAKQP" role="2B76xF">
           <ref role="2B6OnR" to="f8dg:~JCHR_Tells.value()" resolve="value" />
           <node concept="10M0yZ" id="6infEALAKQQ" role="2B70Vg">
-            <ref role="1PxDUh" to="oy3s:6infEALAfer" resolve="AssertBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:6infEALAfer" resolve="AssertPredicate" />
             <ref role="3cqZAo" to="oy3s:6infEALAgS7" resolve="ASSERT" />
           </node>
         </node>
@@ -960,7 +968,7 @@
         <node concept="2B6LJw" id="6infEALAKQZ" role="2B76xF">
           <ref role="2B6OnR" to="f8dg:~JCHR_Asks.value()" resolve="value" />
           <node concept="10M0yZ" id="6infEALAKR0" role="2B70Vg">
-            <ref role="1PxDUh" to="oy3s:6infEALAfer" resolve="AssertBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:6infEALAfer" resolve="AssertPredicate" />
             <ref role="3cqZAo" to="oy3s:6infEALAgS7" resolve="ASSERT" />
           </node>
         </node>
@@ -996,7 +1004,7 @@
         <node concept="2B6LJw" id="6infEALAKRa" role="2B76xF">
           <ref role="2B6OnR" to="f8dg:~JCHR_Asks.value()" resolve="value" />
           <node concept="10M0yZ" id="6infEALAKRb" role="2B70Vg">
-            <ref role="1PxDUh" to="oy3s:6infEALAfer" resolve="AssertBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:6infEALAfer" resolve="AssertPredicate" />
             <ref role="3cqZAo" to="oy3s:6infEALAgS7" resolve="ASSERT" />
           </node>
         </node>
@@ -1073,7 +1081,7 @@
       <node concept="37vLTG" id="4xBopTznZLI" role="3clF46">
         <property role="TrG5h" value="computingSession" />
         <node concept="3uibUv" id="4xBopTznZRE" role="1tU5fm">
-          <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="ComputingSession" />
+          <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="SessionSolver" />
         </node>
       </node>
       <node concept="37vLTG" id="24Vro6cRCEu" role="3clF46">
@@ -1160,7 +1168,7 @@
       <node concept="37vLTG" id="4xBopTzo15x" role="3clF46">
         <property role="TrG5h" value="computingSession" />
         <node concept="3uibUv" id="4xBopTzo1oi" role="1tU5fm">
-          <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="ComputingSession" />
+          <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="SessionSolver" />
         </node>
       </node>
       <node concept="37vLTG" id="5p8T3QHGKJp" role="3clF46">
@@ -1445,7 +1453,7 @@
           </node>
           <node concept="3clFbC" id="4xBopTzpOhS" role="3clFbw">
             <node concept="10M0yZ" id="4xBopTzpOhT" role="3uHU7w">
-              <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+              <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
               <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
             </node>
             <node concept="37vLTw" id="4xBopTzpO$W" role="3uHU7B">
@@ -1741,7 +1749,7 @@
           </node>
           <node concept="3clFbC" id="4xBopTznwQp" role="3clFbw">
             <node concept="10M0yZ" id="4xBopTznx5a" role="3uHU7w">
-              <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+              <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
               <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
             </node>
             <node concept="37vLTw" id="4xBopTzp$oR" role="3uHU7B">
@@ -1792,7 +1800,7 @@
           <ref role="2B6OnR" to="f8dg:~JCHR_Tells.value()" resolve="value" />
           <node concept="10M0yZ" id="6GYQG_SpvAQ" role="2B70Vg">
             <ref role="3cqZAo" to="oy3s:2GO7tyJVob2" resolve="UNI" />
-            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
           </node>
         </node>
       </node>
@@ -2181,7 +2189,7 @@
                           <node concept="liA8E" id="5p8T3QHGZam" role="2OqNvi">
                             <ref role="37wK5l" to="qrld:4xBopTznPKO" resolve="tell" />
                             <node concept="10M0yZ" id="4xBopTzrMis" role="37wK5m">
-                              <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
+                              <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
                               <ref role="3cqZAo" to="oy3s:5uFPQ7C23RV" resolve="EQ_SYM" />
                             </node>
                             <node concept="10QFUN" id="5p8T3QHGZap" role="37wK5m">
@@ -2288,7 +2296,7 @@
                             <node concept="liA8E" id="3HJTsBn83JD" role="2OqNvi">
                               <ref role="37wK5l" to="qrld:4xBopTznPKO" resolve="tell" />
                               <node concept="10M0yZ" id="4xBopTzrMpw" role="37wK5m">
-                                <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
+                                <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
                                 <ref role="3cqZAo" to="oy3s:5uFPQ7C23RV" resolve="EQ_SYM" />
                               </node>
                               <node concept="10QFUN" id="5p8T3QHDoek" role="37wK5m">
@@ -2363,7 +2371,7 @@
           <ref role="2B6OnR" to="f8dg:~JCHR_Tells.value()" resolve="value" />
           <node concept="10M0yZ" id="4U_yxogBZsT" role="2B70Vg">
             <ref role="3cqZAo" to="oy3s:2GO7tyJVob2" resolve="UNI" />
-            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
           </node>
         </node>
       </node>
@@ -2408,7 +2416,7 @@
           <ref role="2B6OnR" to="f8dg:~JCHR_Tells.value()" resolve="value" />
           <node concept="10M0yZ" id="4U_yxogBZLK" role="2B70Vg">
             <ref role="3cqZAo" to="oy3s:2GO7tyJVob2" resolve="UNI" />
-            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
           </node>
         </node>
       </node>
@@ -2577,7 +2585,7 @@
         <node concept="2B6LJw" id="4U_yxogC05Q" role="2B76xF">
           <ref role="2B6OnR" to="f8dg:~JCHR_Tells.value()" resolve="value" />
           <node concept="10M0yZ" id="4U_yxogC05R" role="2B70Vg">
-            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
             <ref role="3cqZAo" to="oy3s:2GO7tyJVob2" resolve="UNI" />
           </node>
         </node>
@@ -3005,7 +3013,7 @@
           <ref role="2B6OnR" to="f8dg:~JCHR_Asks.value()" resolve="value" />
           <node concept="10M0yZ" id="6GYQG_SpvB2" role="2B70Vg">
             <ref role="3cqZAo" to="oy3s:2GO7tyJVob2" resolve="UNI" />
-            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
           </node>
         </node>
       </node>
@@ -3037,7 +3045,7 @@
                 <node concept="liA8E" id="24Vro6cRJN_" role="2OqNvi">
                   <ref role="37wK5l" to="qrld:24Vro6cQCzk" resolve="askFailure" />
                   <node concept="10M0yZ" id="24Vro6cROA3" role="37wK5m">
-                    <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                    <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                     <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
                   </node>
                   <node concept="37vLTw" id="24Vro6cRJSf" role="37wK5m">
@@ -3142,7 +3150,7 @@
             <node concept="liA8E" id="24Vro6cScGO" role="2OqNvi">
               <ref role="37wK5l" to="qrld:24Vro6cQC7A" resolve="askSuccess" />
               <node concept="10M0yZ" id="24Vro6cScGP" role="37wK5m">
-                <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                 <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
               </node>
               <node concept="37vLTw" id="24Vro6cScGQ" role="37wK5m">
@@ -3188,7 +3196,7 @@
           <ref role="2B6OnR" to="f8dg:~JCHR_Asks.value()" resolve="value" />
           <node concept="10M0yZ" id="4U_yxogC1eO" role="2B70Vg">
             <ref role="3cqZAo" to="oy3s:2GO7tyJVob2" resolve="UNI" />
-            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
           </node>
         </node>
       </node>
@@ -3233,7 +3241,7 @@
           <ref role="2B6OnR" to="f8dg:~JCHR_Asks.value()" resolve="value" />
           <node concept="10M0yZ" id="4U_yxogC1Eq" role="2B70Vg">
             <ref role="3cqZAo" to="oy3s:2GO7tyJVob2" resolve="UNI" />
-            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
           </node>
         </node>
       </node>
@@ -3264,7 +3272,7 @@
                 <node concept="liA8E" id="24Vro6cSitX" role="2OqNvi">
                   <ref role="37wK5l" to="qrld:24Vro6cQC7A" resolve="askSuccess" />
                   <node concept="10M0yZ" id="24Vro6cSitY" role="37wK5m">
-                    <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                    <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                     <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
                   </node>
                   <node concept="37vLTw" id="24Vro6cSkqp" role="37wK5m">
@@ -3327,7 +3335,7 @@
                 <node concept="liA8E" id="1MWQR5SpD95" role="2OqNvi">
                   <ref role="37wK5l" to="qrld:24Vro6cQCzk" resolve="askFailure" />
                   <node concept="10M0yZ" id="1MWQR5SpD96" role="37wK5m">
-                    <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                    <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                     <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
                   </node>
                   <node concept="37vLTw" id="1MWQR5SpErK" role="37wK5m">
@@ -3451,7 +3459,7 @@
             <node concept="liA8E" id="24Vro6cS$6F" role="2OqNvi">
               <ref role="37wK5l" to="qrld:24Vro6cQC7A" resolve="askSuccess" />
               <node concept="10M0yZ" id="24Vro6cS$6G" role="37wK5m">
-                <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                 <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
               </node>
               <node concept="37vLTw" id="24Vro6cS$6H" role="37wK5m">
@@ -3497,7 +3505,7 @@
           <ref role="2B6OnR" to="f8dg:~JCHR_Asks.value()" resolve="value" />
           <node concept="10M0yZ" id="4U_yxogC2zE" role="2B70Vg">
             <ref role="3cqZAo" to="oy3s:2GO7tyJVob2" resolve="UNI" />
-            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
           </node>
         </node>
       </node>
@@ -3512,7 +3520,7 @@
                 <node concept="liA8E" id="24Vro6cSpbU" role="2OqNvi">
                   <ref role="37wK5l" to="qrld:24Vro6cQC7A" resolve="askSuccess" />
                   <node concept="10M0yZ" id="24Vro6cSpbV" role="37wK5m">
-                    <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                    <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                     <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
                   </node>
                   <node concept="37vLTw" id="24Vro6cSpbW" role="37wK5m">
@@ -3582,7 +3590,7 @@
                 <node concept="liA8E" id="24Vro6cSqz9" role="2OqNvi">
                   <ref role="37wK5l" to="qrld:24Vro6cQC7A" resolve="askSuccess" />
                   <node concept="10M0yZ" id="24Vro6cSqza" role="37wK5m">
-                    <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                    <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                     <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
                   </node>
                   <node concept="37vLTw" id="24Vro6cSqzb" role="37wK5m">
@@ -3619,7 +3627,7 @@
                 <node concept="liA8E" id="24Vro6cSrVB" role="2OqNvi">
                   <ref role="37wK5l" to="qrld:24Vro6cQC7A" resolve="askSuccess" />
                   <node concept="10M0yZ" id="24Vro6cSrVC" role="37wK5m">
-                    <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                    <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                     <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
                   </node>
                   <node concept="37vLTw" id="24Vro6cSrVD" role="37wK5m">
@@ -3700,7 +3708,7 @@
                 <node concept="liA8E" id="1MWQR5SpIjz" role="2OqNvi">
                   <ref role="37wK5l" to="qrld:24Vro6cQCzk" resolve="askFailure" />
                   <node concept="10M0yZ" id="1MWQR5SpIj$" role="37wK5m">
-                    <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                    <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                     <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
                   </node>
                   <node concept="37vLTw" id="1MWQR5SpJEg" role="37wK5m">
@@ -3839,7 +3847,7 @@
             <node concept="liA8E" id="24Vro6cSweV" role="2OqNvi">
               <ref role="37wK5l" to="qrld:24Vro6cQC7A" resolve="askSuccess" />
               <node concept="10M0yZ" id="24Vro6cSweW" role="37wK5m">
-                <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                 <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
               </node>
               <node concept="37vLTw" id="24Vro6cSweX" role="37wK5m">
@@ -4176,7 +4184,7 @@
                 <node concept="liA8E" id="6xYPVrpAQ$f" role="2OqNvi">
                   <ref role="37wK5l" to="qrld:4xBopTznHV5" resolve="ask" />
                   <node concept="10M0yZ" id="4xBopTzrNsC" role="37wK5m">
-                    <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
+                    <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
                     <ref role="3cqZAo" to="oy3s:5uFPQ7C23RV" resolve="EQ_SYM" />
                   </node>
                   <node concept="37vLTw" id="6xYPVrpAQ$i" role="37wK5m">
@@ -4228,7 +4236,7 @@
                   <node concept="liA8E" id="6xYPVrpAY27" role="2OqNvi">
                     <ref role="37wK5l" to="qrld:4xBopTznHV5" resolve="ask" />
                     <node concept="10M0yZ" id="4xBopTzrMvx" role="37wK5m">
-                      <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
+                      <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
                       <ref role="3cqZAo" to="oy3s:5uFPQ7C23RV" resolve="EQ_SYM" />
                     </node>
                     <node concept="37vLTw" id="6xYPVrpAY2a" role="37wK5m">
@@ -4650,7 +4658,7 @@
       <property role="TrG5h" value="computingSession" />
       <node concept="3Tm6S6" id="4xBopTznWR$" role="1B3o_S" />
       <node concept="3uibUv" id="4xBopTznYl8" role="1tU5fm">
-        <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="ComputingSession" />
+        <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="SessionSolver" />
       </node>
     </node>
     <node concept="312cEg" id="4U_yxogDGOE" role="jymVt">
@@ -4695,7 +4703,7 @@
           <ref role="2B6OnR" to="f8dg:~JCHR_Tells.value()" resolve="value" />
           <node concept="10M0yZ" id="4OsiK2BALzP" role="2B70Vg">
             <ref role="3cqZAo" to="oy3s:2GO7tyJVob2" resolve="UNI" />
-            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
           </node>
         </node>
       </node>
@@ -4725,7 +4733,7 @@
           <ref role="2B6OnR" to="f8dg:~JCHR_Tells.value()" resolve="value" />
           <node concept="10M0yZ" id="4U_yxogCcGS" role="2B70Vg">
             <ref role="3cqZAo" to="oy3s:2GO7tyJVob2" resolve="UNI" />
-            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
           </node>
         </node>
       </node>
@@ -4755,7 +4763,7 @@
           <ref role="2B6OnR" to="f8dg:~JCHR_Tells.value()" resolve="value" />
           <node concept="10M0yZ" id="4U_yxogCdk6" role="2B70Vg">
             <ref role="3cqZAo" to="oy3s:2GO7tyJVob2" resolve="UNI" />
-            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
           </node>
         </node>
       </node>
@@ -4785,7 +4793,7 @@
           <ref role="2B6OnR" to="f8dg:~JCHR_Tells.value()" resolve="value" />
           <node concept="10M0yZ" id="4U_yxogCeA4" role="2B70Vg">
             <ref role="3cqZAo" to="oy3s:2GO7tyJVob2" resolve="UNI" />
-            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
           </node>
         </node>
       </node>
@@ -4815,7 +4823,7 @@
           <ref role="2B6OnR" to="f8dg:~JCHR_Asks.value()" resolve="value" />
           <node concept="10M0yZ" id="4OsiK2BALAQ" role="2B70Vg">
             <ref role="3cqZAo" to="oy3s:2GO7tyJVob2" resolve="UNI" />
-            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
           </node>
         </node>
       </node>
@@ -4845,7 +4853,7 @@
           <ref role="2B6OnR" to="f8dg:~JCHR_Asks.value()" resolve="value" />
           <node concept="10M0yZ" id="4U_yxogC9UR" role="2B70Vg">
             <ref role="3cqZAo" to="oy3s:2GO7tyJVob2" resolve="UNI" />
-            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
           </node>
         </node>
       </node>
@@ -4875,7 +4883,7 @@
           <ref role="2B6OnR" to="f8dg:~JCHR_Asks.value()" resolve="value" />
           <node concept="10M0yZ" id="4U_yxogCan7" role="2B70Vg">
             <ref role="3cqZAo" to="oy3s:2GO7tyJVob2" resolve="UNI" />
-            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
           </node>
         </node>
       </node>
@@ -4905,7 +4913,7 @@
           <ref role="2B6OnR" to="f8dg:~JCHR_Asks.value()" resolve="value" />
           <node concept="10M0yZ" id="4U_yxogCbuN" role="2B70Vg">
             <ref role="3cqZAo" to="oy3s:2GO7tyJVob2" resolve="UNI" />
-            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
           </node>
         </node>
       </node>
@@ -4922,7 +4930,7 @@
               <ref role="2B6OnR" to="f8dg:~JCHR_Constraint.identifier()" resolve="identifier" />
               <node concept="10M0yZ" id="4OsiK2BALdr" role="2B70Vg">
                 <ref role="3cqZAo" to="oy3s:2GO7tyJVob2" resolve="UNI" />
-                <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
               </node>
             </node>
             <node concept="2B6LJw" id="6njqcfQWwks" role="2B76xF">
@@ -4935,7 +4943,7 @@
               <ref role="2B6OnR" to="f8dg:~JCHR_Constraint.infix()" resolve="infix" />
               <node concept="10M0yZ" id="5lJXKvHNj" role="2B70Vg">
                 <ref role="3cqZAo" to="oy3s:2GO7tyJVob6" resolve="INFIX_UNI" />
-                <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
               </node>
             </node>
             <node concept="2B6LJw" id="6njqcfQWwzK" role="2B76xF">
@@ -4979,7 +4987,7 @@
         <node concept="2B6LJw" id="3HJTsBn4xBt" role="2B76xF">
           <ref role="2B6OnR" to="f8dg:~JCHR_Tells.value()" resolve="value" />
           <node concept="10M0yZ" id="3HJTsBn4EEH" role="2B70Vg">
-            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
             <ref role="3cqZAo" to="oy3s:3HJTsBn4kQi" resolve="EQ" />
           </node>
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@@ -5009,7 +5017,7 @@
         <node concept="2B6LJw" id="3HJTsBn4xBF" role="2B76xF">
           <ref role="2B6OnR" to="f8dg:~JCHR_Tells.value()" resolve="value" />
           <node concept="10M0yZ" id="3HJTsBn4F8f" role="2B70Vg">
-            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
             <ref role="3cqZAo" to="oy3s:3HJTsBn4kQi" resolve="EQ" />
           </node>
         </node>
@@ -5040,7 +5048,7 @@
           <ref role="2B6OnR" to="f8dg:~JCHR_Tells.value()" resolve="value" />
           <node concept="10M0yZ" id="3HJTsBn4Fuw" role="2B70Vg">
             <ref role="3cqZAo" to="oy3s:3HJTsBn4kQi" resolve="EQ" />
-            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
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@@ -5069,7 +5077,7 @@
         <node concept="2B6LJw" id="3HJTsBn4xC7" role="2B76xF">
           <ref role="2B6OnR" to="f8dg:~JCHR_Tells.value()" resolve="value" />
           <node concept="10M0yZ" id="3HJTsBn4FOM" role="2B70Vg">
-            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
             <ref role="3cqZAo" to="oy3s:3HJTsBn4kQi" resolve="EQ" />
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         </node>
@@ -5100,7 +5108,7 @@
           <ref role="2B6OnR" to="f8dg:~JCHR_Asks.value()" resolve="value" />
           <node concept="10M0yZ" id="3HJTsBn4Gb3" role="2B70Vg">
             <ref role="3cqZAo" to="oy3s:3HJTsBn4kQi" resolve="EQ" />
-            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
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@@ -5129,7 +5137,7 @@
         <node concept="2B6LJw" id="3HJTsBn4xCz" role="2B76xF">
           <ref role="2B6OnR" to="f8dg:~JCHR_Asks.value()" resolve="value" />
           <node concept="10M0yZ" id="3HJTsBn4Gxk" role="2B70Vg">
-            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
             <ref role="3cqZAo" to="oy3s:3HJTsBn4kQi" resolve="EQ" />
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@@ -5159,7 +5167,7 @@
         <node concept="2B6LJw" id="3HJTsBn4xCL" role="2B76xF">
           <ref role="2B6OnR" to="f8dg:~JCHR_Asks.value()" resolve="value" />
           <node concept="10M0yZ" id="3HJTsBn4GR_" role="2B70Vg">
-            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
             <ref role="3cqZAo" to="oy3s:3HJTsBn4kQi" resolve="EQ" />
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@@ -5190,7 +5198,7 @@
           <ref role="2B6OnR" to="f8dg:~JCHR_Asks.value()" resolve="value" />
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             <ref role="3cqZAo" to="oy3s:3HJTsBn4kQi" resolve="EQ" />
-            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
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@@ -5207,7 +5215,7 @@
             <node concept="2B6LJw" id="3HJTsBn4BXf" role="2B76xF">
               <ref role="2B6OnR" to="f8dg:~JCHR_Constraint.identifier()" resolve="identifier" />
               <node concept="10M0yZ" id="3HJTsBn4BXg" role="2B70Vg">
-                <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
+                <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
                 <ref role="3cqZAo" to="oy3s:3HJTsBn4kQi" resolve="EQ" />
               </node>
             </node>
@@ -5220,7 +5228,7 @@
             <node concept="2B6LJw" id="3HJTsBn4BXj" role="2B76xF">
               <ref role="2B6OnR" to="f8dg:~JCHR_Constraint.infix()" resolve="infix" />
               <node concept="10M0yZ" id="3HJTsBn4BXk" role="2B70Vg">
-                <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
+                <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
                 <ref role="3cqZAo" to="oy3s:3HJTsBn4kQn" resolve="INFIX_EQ" />
               </node>
             </node>
@@ -5260,7 +5268,7 @@
       <node concept="37vLTG" id="3HJTsBn5dln" role="3clF46">
         <property role="TrG5h" value="computingSession" />
         <node concept="3uibUv" id="4xBopTzoKGe" role="1tU5fm">
-          <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="ComputingSession" />
+          <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="SessionSolver" />
         </node>
       </node>
     </node>
@@ -5299,7 +5307,7 @@
       <node concept="37vLTG" id="5p8T3QHE69z" role="3clF46">
         <property role="TrG5h" value="computingSession" />
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-          <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="ComputingSession" />
+          <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="SessionSolver" />
         </node>
       </node>
       <node concept="37vLTG" id="5p8T3QHE69_" role="3clF46">
@@ -5309,7 +5317,7 @@
         </node>
       </node>
     </node>
-    <node concept="2tJIrI" id="3HJTsBn52W4" role="jymVt" />
+    <node concept="2tJIrI" id="2tcGHBEqkLH" role="jymVt" />
     <node concept="3clFb_" id="4xBopTzoSXw" role="jymVt">
       <property role="1EzhhJ" value="false" />
       <property role="TrG5h" value="ask" />
@@ -5575,7 +5583,7 @@
           </node>
           <node concept="3clFbC" id="4xBopTzpU_6" role="3clFbw">
             <node concept="10M0yZ" id="4xBopTzpU_7" role="3uHU7w">
-              <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
+              <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
               <ref role="3cqZAo" to="oy3s:5uFPQ7C23RV" resolve="EQ_SYM" />
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             <node concept="37vLTw" id="4xBopTzpU_8" role="3uHU7B">
@@ -5868,7 +5876,7 @@
           </node>
           <node concept="3clFbC" id="4xBopTzqudZ" role="3clFbw">
             <node concept="10M0yZ" id="4xBopTzque0" role="3uHU7w">
-              <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
+              <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
               <ref role="3cqZAo" to="oy3s:5uFPQ7C23RV" resolve="EQ_SYM" />
             </node>
             <node concept="37vLTw" id="4xBopTzqvb$" role="3uHU7B">
@@ -5918,7 +5926,7 @@
         <node concept="2B6LJw" id="3HJTsBn4V_j" role="2B76xF">
           <ref role="2B6OnR" to="f8dg:~JCHR_Tells.value()" resolve="value" />
           <node concept="10M0yZ" id="3HJTsBn4V_k" role="2B70Vg">
-            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
             <ref role="3cqZAo" to="oy3s:3HJTsBn4kQi" resolve="EQ" />
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@@ -6058,7 +6066,7 @@
         <node concept="2B6LJw" id="3HJTsBn4V_y" role="2B76xF">
           <ref role="2B6OnR" to="f8dg:~JCHR_Tells.value()" resolve="value" />
           <node concept="10M0yZ" id="3HJTsBn4V_z" role="2B70Vg">
-            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
             <ref role="3cqZAo" to="oy3s:3HJTsBn4kQi" resolve="EQ" />
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@@ -6104,7 +6112,7 @@
           <ref role="2B6OnR" to="f8dg:~JCHR_Tells.value()" resolve="value" />
           <node concept="10M0yZ" id="3HJTsBn4V_M" role="2B70Vg">
             <ref role="3cqZAo" to="oy3s:3HJTsBn4kQi" resolve="EQ" />
-            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
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@@ -6286,7 +6294,7 @@
         <node concept="2B6LJw" id="3HJTsBn4VA1" role="2B76xF">
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           <node concept="10M0yZ" id="3HJTsBn4VA2" role="2B70Vg">
-            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
             <ref role="3cqZAo" to="oy3s:3HJTsBn4kQi" resolve="EQ" />
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@@ -6757,7 +6765,7 @@
           <ref role="2B6OnR" to="f8dg:~JCHR_Asks.value()" resolve="value" />
           <node concept="10M0yZ" id="3HJTsBn4VAg" role="2B70Vg">
             <ref role="3cqZAo" to="oy3s:3HJTsBn4kQi" resolve="EQ" />
-            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
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@@ -6817,7 +6825,7 @@
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           <node concept="10M0yZ" id="3HJTsBn4VAx" role="2B70Vg">
-            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
             <ref role="3cqZAo" to="oy3s:3HJTsBn4kQi" resolve="EQ" />
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@@ -6862,7 +6870,7 @@
         <node concept="2B6LJw" id="3HJTsBn4VAL" role="2B76xF">
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           <node concept="10M0yZ" id="3HJTsBn4VAM" role="2B70Vg">
-            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
             <ref role="3cqZAo" to="oy3s:3HJTsBn4kQi" resolve="EQ" />
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@@ -6954,7 +6962,7 @@
           <ref role="2B6OnR" to="f8dg:~JCHR_Asks.value()" resolve="value" />
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             <ref role="3cqZAo" to="oy3s:3HJTsBn4kQi" resolve="EQ" />
-            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
+            <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
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         </node>
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@@ -7338,7 +7346,7 @@
       <property role="TrG5h" value="computingSession" />
       <node concept="3Tm6S6" id="4xBopTzoHc$" role="1B3o_S" />
       <node concept="3uibUv" id="4xBopTzoIhj" role="1tU5fm">
-        <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="ComputingSession" />
+        <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="SessionSolver" />
       </node>
     </node>
     <node concept="312cEg" id="3HJTsBn53Hy" role="jymVt">
@@ -7688,7 +7696,7 @@
           </node>
         </node>
       </node>
-      <node concept="2tJIrI" id="7ISVfSJ1k5" role="jymVt" />
+      <node concept="2tJIrI" id="2tcGHBEqput" role="jymVt" />
       <node concept="3Tm1VV" id="7ISVfSJ0DG" role="1B3o_S" />
       <node concept="3uibUv" id="7ISVfSJ10y" role="1zkMxy">
         <ref role="3uigEE" node="4xBopTzrd8Y" resolve="LogicalSolverImpl" />
@@ -7733,7 +7741,7 @@
           </node>
         </node>
       </node>
-      <node concept="2tJIrI" id="7ISVfSJ1oy" role="jymVt" />
+      <node concept="2tJIrI" id="2tcGHBEvoB2" role="jymVt" />
       <node concept="3Tm1VV" id="7ISVfSJ1oz" role="1B3o_S" />
       <node concept="3uibUv" id="7ISVfSJ1o$" role="1zkMxy">
         <ref role="3uigEE" node="4xBopTzrd8Y" resolve="LogicalSolverImpl" />
@@ -8487,96 +8495,20 @@
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   <node concept="312cEu" id="7ISVfSIxNO">
     <property role="2bfB8j" value="false" />
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-    <node concept="2tJIrI" id="7ISVfSIy3T" role="jymVt" />
-    <node concept="3clFbW" id="5mr7UHch7og" role="jymVt">
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-              <node concept="2OwXpG" id="5mr7UHch9IB" role="2OqNvi">
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-            <ref role="3cqZAo" node="5jPBdK_Ahj" resolve="predicateSymbols" />
-          </node>
-        </node>
-      </node>
-    </node>
+    <property role="TrG5h" value="JchrSolver" />
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     <node concept="3clFb_" id="7ISVfSIy6a" role="jymVt">
-      <property role="TrG5h" value="register" />
+      <property role="TrG5h" value="registerSymbol" />
       <node concept="37vLTG" id="7ISVfSIJee" role="3clF46">
         <property role="TrG5h" value="symbol" />
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-          <ref role="3uigEE" to="qrld:5uFPQ7B$mzX" resolve="Symbol" />
+        <node concept="3uibUv" id="2tcGHBEei$8" role="1tU5fm">
+          <ref role="3uigEE" to="qrld:5uFPQ7B$$3f" resolve="PredicateSymbol" />
+        </node>
+      </node>
+      <node concept="37vLTG" id="2tcGHBEisRf" role="3clF46">
+        <property role="TrG5h" value="computingTracer" />
+        <node concept="3uibUv" id="2tcGHBEisZb" role="1tU5fm">
+          <ref role="3uigEE" to="qrld:24Vro6cQnrj" resolve="ComputingTracer" />
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       </node>
       <node concept="3cqZAl" id="7ISVfSIy6c" role="3clF45" />
@@ -8587,9 +8519,7 @@
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             <node concept="3clFbF" id="7ISVfSIVrg" role="3cqZAp">
               <node concept="2OqwBi" id="7ISVfSIVrQ" role="3clFbG">
-                <node concept="37vLTw" id="7ISVfSIVrf" role="2Oq$k0">
-                  <ref role="3cqZAo" node="5mr7UHch7DV" resolve="computingSession" />
-                </node>
+                <node concept="Xjq3P" id="2tcGHBEecgK" role="2Oq$k0" />
                 <node concept="liA8E" id="7ISVfSIVsU" role="2OqNvi">
                   <ref role="37wK5l" to="qrld:6Kcfpq7B2LV" resolve="registerSolver" />
                   <node concept="10QFUN" id="7ISVfSIYFl" role="37wK5m">
@@ -8603,11 +8533,9 @@
                   <node concept="2ShNRf" id="7ISVfSIVIp" role="37wK5m">
                     <node concept="1pGfFk" id="7ISVfSIWk9" role="2ShVmc">
                       <ref role="37wK5l" node="3HJTsBn5KhD" resolve="UnificationSolverImpl" />
-                      <node concept="37vLTw" id="5mr7UHchbwX" role="37wK5m">
-                        <ref role="3cqZAo" node="5mr7UHch7DV" resolve="computingSession" />
-                      </node>
+                      <node concept="Xjq3P" id="2tcGHBEecLr" role="37wK5m" />
                       <node concept="37vLTw" id="5mr7UHchcsc" role="37wK5m">
-                        <ref role="3cqZAo" node="5mr7UHchbU9" resolve="computingTracer" />
+                        <ref role="3cqZAo" node="2tcGHBEisRf" resolve="computingTracer" />
                       </node>
                     </node>
                   </node>
@@ -8618,7 +8546,7 @@
           </node>
           <node concept="2OqwBi" id="7ISVfSIJwN" role="3clFbw">
             <node concept="10M0yZ" id="7ISVfSIJ9U" role="2Oq$k0">
-              <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+              <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
               <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
             </node>
             <node concept="liA8E" id="7ISVfSIJyd" role="2OqNvi">
@@ -8631,7 +8559,7 @@
           <node concept="3eNFk2" id="7ISVfSIJml" role="3eNLev">
             <node concept="2OqwBi" id="7ISVfSIJ_2" role="3eO9$A">
               <node concept="10M0yZ" id="7ISVfSIJrd" role="2Oq$k0">
-                <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
+                <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
                 <ref role="3cqZAo" to="oy3s:5uFPQ7C23RV" resolve="EQ_SYM" />
               </node>
               <node concept="liA8E" id="7ISVfSIJAs" role="2OqNvi">
@@ -8644,9 +8572,7 @@
             <node concept="3clFbS" id="7ISVfSIJmn" role="3eOfB_">
               <node concept="3clFbF" id="7ISVfSIYOv" role="3cqZAp">
                 <node concept="2OqwBi" id="7ISVfSIYOw" role="3clFbG">
-                  <node concept="37vLTw" id="7ISVfSIYOx" role="2Oq$k0">
-                    <ref role="3cqZAo" node="5mr7UHch7DV" resolve="computingSession" />
-                  </node>
+                  <node concept="Xjq3P" id="2tcGHBEecj3" role="2Oq$k0" />
                   <node concept="liA8E" id="7ISVfSIYOy" role="2OqNvi">
                     <ref role="37wK5l" to="qrld:6Kcfpq7B2LV" resolve="registerSolver" />
                     <node concept="10QFUN" id="7ISVfSIYOz" role="37wK5m">
@@ -8660,9 +8586,7 @@
                     <node concept="2ShNRf" id="7ISVfSIYOA" role="37wK5m">
                       <node concept="1pGfFk" id="7ISVfSIYOB" role="2ShVmc">
                         <ref role="37wK5l" node="3HJTsBn5dl7" resolve="EqualsSolverImpl" />
-                        <node concept="37vLTw" id="7ISVfSIYOD" role="37wK5m">
-                          <ref role="3cqZAo" node="5mr7UHch7DV" resolve="computingSession" />
-                        </node>
+                        <node concept="Xjq3P" id="2tcGHBEecMU" role="37wK5m" />
                       </node>
                     </node>
                   </node>
@@ -8674,7 +8598,7 @@
           <node concept="3eNFk2" id="7ISVfSIJuG" role="3eNLev">
             <node concept="2OqwBi" id="7ISVfSIJGK" role="3eO9$A">
               <node concept="10M0yZ" id="7ISVfSIJCI" role="2Oq$k0">
-                <ref role="1PxDUh" to="oy3s:6infEALAfer" resolve="AssertBuiltinConstraint" />
+                <ref role="1PxDUh" to="oy3s:6infEALAfer" resolve="AssertPredicate" />
                 <ref role="3cqZAo" to="oy3s:5uFPQ7BZnLB" resolve="ASSERT_SYM" />
               </node>
               <node concept="liA8E" id="7ISVfSIJIa" role="2OqNvi">
@@ -8687,9 +8611,7 @@
             <node concept="3clFbS" id="7ISVfSIJuI" role="3eOfB_">
               <node concept="3clFbF" id="7ISVfSIZhm" role="3cqZAp">
                 <node concept="2OqwBi" id="7ISVfSIZhn" role="3clFbG">
-                  <node concept="37vLTw" id="7ISVfSIZho" role="2Oq$k0">
-                    <ref role="3cqZAo" node="5mr7UHch7DV" resolve="computingSession" />
-                  </node>
+                  <node concept="Xjq3P" id="2tcGHBEeclc" role="2Oq$k0" />
                   <node concept="liA8E" id="7ISVfSIZhp" role="2OqNvi">
                     <ref role="37wK5l" to="qrld:6Kcfpq7B2LV" resolve="registerSolver" />
                     <node concept="10QFUN" id="7ISVfSIZhq" role="37wK5m">
@@ -8714,7 +8636,7 @@
           <node concept="3eNFk2" id="7ISVfSIJJE" role="3eNLev">
             <node concept="2OqwBi" id="7ISVfSIJJF" role="3eO9$A">
               <node concept="10M0yZ" id="7ISVfSIK8M" role="2Oq$k0">
-                <ref role="1PxDUh" to="xq5w:5$WbtTOYoMb" resolve="LogicalBuiltinConstraint" />
+                <ref role="1PxDUh" to="xq5w:5$WbtTOYoMb" resolve="LogicalPredicate" />
                 <ref role="3cqZAo" to="xq5w:5uFPQ7C26$b" resolve="BOUND_SYM" />
               </node>
               <node concept="liA8E" id="7ISVfSIJJH" role="2OqNvi">
@@ -8727,9 +8649,7 @@
             <node concept="3clFbS" id="7ISVfSIJJJ" role="3eOfB_">
               <node concept="3clFbF" id="7ISVfSJ2P6" role="3cqZAp">
                 <node concept="2OqwBi" id="7ISVfSJ2P7" role="3clFbG">
-                  <node concept="37vLTw" id="7ISVfSJ2P8" role="2Oq$k0">
-                    <ref role="3cqZAo" node="5mr7UHch7DV" resolve="computingSession" />
-                  </node>
+                  <node concept="Xjq3P" id="2tcGHBEecmS" role="2Oq$k0" />
                   <node concept="liA8E" id="7ISVfSJ2P9" role="2OqNvi">
                     <ref role="37wK5l" to="qrld:6Kcfpq7B2LV" resolve="registerSolver" />
                     <node concept="10QFUN" id="7ISVfSJ2Pa" role="37wK5m">
@@ -8754,7 +8674,7 @@
           <node concept="3eNFk2" id="7ISVfSJ2Gd" role="3eNLev">
             <node concept="2OqwBi" id="7ISVfSJ2Ge" role="3eO9$A">
               <node concept="10M0yZ" id="7ISVfSJ2Gf" role="2Oq$k0">
-                <ref role="1PxDUh" to="xq5w:5$WbtTOYoMb" resolve="LogicalBuiltinConstraint" />
+                <ref role="1PxDUh" to="xq5w:5$WbtTOYoMb" resolve="LogicalPredicate" />
                 <ref role="3cqZAo" to="xq5w:5uFPQ7C279$" resolve="FREE_SYM" />
               </node>
               <node concept="liA8E" id="7ISVfSJ2Gg" role="2OqNvi">
@@ -8767,9 +8687,7 @@
             <node concept="3clFbS" id="7ISVfSJ2Gi" role="3eOfB_">
               <node concept="3clFbF" id="7ISVfSJ30n" role="3cqZAp">
                 <node concept="2OqwBi" id="7ISVfSJ30o" role="3clFbG">
-                  <node concept="37vLTw" id="7ISVfSJ30p" role="2Oq$k0">
-                    <ref role="3cqZAo" node="5mr7UHch7DV" resolve="computingSession" />
-                  </node>
+                  <node concept="Xjq3P" id="2tcGHBEecoN" role="2Oq$k0" />
                   <node concept="liA8E" id="7ISVfSJ30q" role="2OqNvi">
                     <ref role="37wK5l" to="qrld:6Kcfpq7B2LV" resolve="registerSolver" />
                     <node concept="10QFUN" id="7ISVfSJ30r" role="37wK5m">
@@ -8813,112 +8731,203 @@
         </node>
         <node concept="3clFbH" id="5mr7UHcbFmH" role="3cqZAp" />
       </node>
+      <node concept="2AHcQZ" id="2tcGHBEej41" role="2AJF6D">
+        <ref role="2AI5Lk" to="wyt6:~Override" resolve="Override" />
+      </node>
     </node>
-    <node concept="2tJIrI" id="5mr7UHch7aO" role="jymVt" />
-    <node concept="3clFb_" id="6Kcfpq7Bs88" role="jymVt">
-      <property role="TrG5h" value="registerHandler" />
-      <node concept="37vLTG" id="7ISVfSIOyP" role="3clF46">
+    <node concept="2tJIrI" id="2tcGHBEvc5Q" role="jymVt" />
+    <node concept="3clFb_" id="2tcGHBEvbMG" role="jymVt">
+      <property role="TrG5h" value="solverClass" />
+      <node concept="37vLTG" id="2tcGHBEvbMH" role="3clF46">
         <property role="TrG5h" value="symbol" />
-        <node concept="3uibUv" id="7ISVfSIOGX" role="1tU5fm">
-          <ref role="3uigEE" to="qrld:5uFPQ7B$mzX" resolve="Symbol" />
-        </node>
-      </node>
-      <node concept="37vLTG" id="6Kcfpq7BtOW" role="3clF46">
-        <property role="TrG5h" value="instructible" />
-        <node concept="3uibUv" id="6Kcfpq7BtZc" role="1tU5fm">
-          <ref role="3uigEE" to="qrld:6Kcfpq7AXVG" resolve="Instructible" />
-        </node>
-      </node>
-      <node concept="3cqZAl" id="6Kcfpq7Bs8a" role="3clF45" />
-      <node concept="3Tmbuc" id="6Kcfpq7BskN" role="1B3o_S" />
-      <node concept="3clFbS" id="6Kcfpq7Bs8c" role="3clF47">
-        <node concept="3clFbF" id="6Kcfpq7Bu1B" role="3cqZAp">
-          <node concept="2OqwBi" id="6Kcfpq7Bu22" role="3clFbG">
-            <node concept="37vLTw" id="7ISVfSIOWI" role="2Oq$k0">
-              <ref role="3cqZAo" node="5mr7UHch7DV" resolve="computingSession" />
-            </node>
-            <node concept="liA8E" id="6Kcfpq7Bu2G" role="2OqNvi">
-              <ref role="37wK5l" to="qrld:6Kcfpq7B2yH" resolve="registerHandler" />
-              <node concept="37vLTw" id="7ISVfSIOLP" role="37wK5m">
-                <ref role="3cqZAo" node="7ISVfSIOyP" resolve="symbol" />
-              </node>
-              <node concept="37vLTw" id="6Kcfpq7Bu3W" role="37wK5m">
-                <ref role="3cqZAo" node="6Kcfpq7BtOW" resolve="instructible" />
-              </node>
-            </node>
-          </node>
-        </node>
-      </node>
-    </node>
-    <node concept="2tJIrI" id="6Kcfpq7BuLv" role="jymVt" />
-    <node concept="3clFb_" id="6Kcfpq7Buzk" role="jymVt">
-      <property role="TrG5h" value="registerSolver" />
-      <node concept="37vLTG" id="7ISVfSIOZm" role="3clF46">
-        <property role="TrG5h" value="predicateSymbol" />
-        <node concept="3uibUv" id="7ISVfSIPw0" role="1tU5fm">
+        <node concept="3uibUv" id="2tcGHBEvbMI" role="1tU5fm">
           <ref role="3uigEE" to="qrld:5uFPQ7B$$3f" resolve="PredicateSymbol" />
         </node>
       </node>
-      <node concept="37vLTG" id="6Kcfpq7Buzn" role="3clF46">
-        <property role="TrG5h" value="queryable" />
-        <node concept="3uibUv" id="6Kcfpq7Bw2C" role="1tU5fm">
-          <ref role="3uigEE" to="qrld:6Kcfpq7AYBh" resolve="Queryable" />
+      <node concept="3uibUv" id="2tcGHBEvcMg" role="3clF45">
+        <ref role="3uigEE" to="wyt6:~Class" resolve="Class" />
+        <node concept="3qUE_q" id="2tcGHBEvcY3" role="11_B2D">
+          <node concept="3uibUv" id="2tcGHBEvcZz" role="3qUE_r">
+            <ref role="3uigEE" to="qrld:6Kcfpq7AYBh" resolve="Queryable" />
+          </node>
         </node>
       </node>
-      <node concept="3cqZAl" id="6Kcfpq7Buzp" role="3clF45" />
-      <node concept="3Tmbuc" id="6Kcfpq7Buzq" role="1B3o_S" />
-      <node concept="3clFbS" id="6Kcfpq7Buzr" role="3clF47">
-        <node concept="3clFbF" id="6Kcfpq7Buzs" role="3cqZAp">
-          <node concept="2OqwBi" id="6Kcfpq7Buzt" role="3clFbG">
-            <node concept="37vLTw" id="7ISVfSIPqq" role="2Oq$k0">
-              <ref role="3cqZAo" node="5mr7UHch7DV" resolve="computingSession" />
-            </node>
-            <node concept="liA8E" id="6Kcfpq7Buzv" role="2OqNvi">
-              <ref role="37wK5l" to="qrld:6Kcfpq7B2LV" resolve="registerSolver" />
-              <node concept="37vLTw" id="7ISVfSIPef" role="37wK5m">
-                <ref role="3cqZAo" node="7ISVfSIOZm" resolve="predicateSymbol" />
+      <node concept="3Tm1VV" id="2tcGHBEvj$1" role="1B3o_S" />
+      <node concept="3clFbS" id="2tcGHBEvbMN" role="3clF47">
+        <node concept="3clFbH" id="2tcGHBEvbMO" role="3cqZAp" />
+        <node concept="3clFbJ" id="2tcGHBEvbMP" role="3cqZAp">
+          <node concept="3clFbS" id="2tcGHBEvbMQ" role="3clFbx">
+            <node concept="3cpWs6" id="2tcGHBEvfUa" role="3cqZAp">
+              <node concept="3VsKOn" id="2tcGHBEvgfM" role="3cqZAk">
+                <ref role="3VsUkX" node="6njqcfQVO0n" resolve="UnificationSolver" />
               </node>
-              <node concept="37vLTw" id="6Kcfpq7Buzx" role="37wK5m">
-                <ref role="3cqZAo" node="6Kcfpq7Buzn" resolve="queryable" />
-              </node>
-            </node>
-          </node>
-        </node>
-        <node concept="3clFbF" id="4xBopTzylBh" role="3cqZAp">
-          <node concept="2OqwBi" id="4xBopTzylBi" role="3clFbG">
-            <node concept="37vLTw" id="7ISVfSIPtf" role="2Oq$k0">
-              <ref role="3cqZAo" node="5mr7UHch7DV" resolve="computingSession" />
-            </node>
-            <node concept="liA8E" id="4xBopTzylBk" role="2OqNvi">
-              <ref role="37wK5l" to="qrld:6Kcfpq7B2yH" resolve="registerHandler" />
-              <node concept="37vLTw" id="7ISVfSIPfC" role="37wK5m">
-                <ref role="3cqZAo" node="7ISVfSIOZm" resolve="predicateSymbol" />
-              </node>
-              <node concept="37vLTw" id="4xBopTzylH0" role="37wK5m">
-                <ref role="3cqZAo" node="6Kcfpq7Buzn" resolve="queryable" />
+            </node>
+            <node concept="3clFbH" id="2tcGHBEvgqn" role="3cqZAp" />
+          </node>
+          <node concept="2OqwBi" id="2tcGHBEvbN3" role="3clFbw">
+            <node concept="10M0yZ" id="2tcGHBEvbN4" role="2Oq$k0">
+              <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
+              <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
+            </node>
+            <node concept="liA8E" id="2tcGHBEvbN5" role="2OqNvi">
+              <ref role="37wK5l" to="qrld:54i3Fxd17bK" resolve="equals" />
+              <node concept="37vLTw" id="2tcGHBEvbN6" role="37wK5m">
+                <ref role="3cqZAo" node="2tcGHBEvbMH" resolve="symbol" />
+              </node>
+            </node>
+          </node>
+          <node concept="3eNFk2" id="2tcGHBEvbN7" role="3eNLev">
+            <node concept="2OqwBi" id="2tcGHBEvbN8" role="3eO9$A">
+              <node concept="10M0yZ" id="2tcGHBEvbN9" role="2Oq$k0">
+                <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
+                <ref role="3cqZAo" to="oy3s:5uFPQ7C23RV" resolve="EQ_SYM" />
+              </node>
+              <node concept="liA8E" id="2tcGHBEvbNa" role="2OqNvi">
+                <ref role="37wK5l" to="qrld:54i3Fxd17bK" resolve="equals" />
+                <node concept="37vLTw" id="2tcGHBEvbNb" role="37wK5m">
+                  <ref role="3cqZAo" node="2tcGHBEvbMH" resolve="symbol" />
+                </node>
+              </node>
+            </node>
+            <node concept="3clFbS" id="2tcGHBEvbNc" role="3eOfB_">
+              <node concept="3cpWs6" id="2tcGHBEvgBd" role="3cqZAp">
+                <node concept="3VsKOn" id="2tcGHBEvh5M" role="3cqZAk">
+                  <ref role="3VsUkX" node="3HJTsBn4mEA" resolve="EqualsSolver" />
+                </node>
+              </node>
+              <node concept="3clFbH" id="2tcGHBEvbNn" role="3cqZAp" />
+            </node>
+          </node>
+          <node concept="3eNFk2" id="2tcGHBEvbNo" role="3eNLev">
+            <node concept="2OqwBi" id="2tcGHBEvbNp" role="3eO9$A">
+              <node concept="10M0yZ" id="2tcGHBEvbNq" role="2Oq$k0">
+                <ref role="1PxDUh" to="oy3s:6infEALAfer" resolve="AssertPredicate" />
+                <ref role="3cqZAo" to="oy3s:5uFPQ7BZnLB" resolve="ASSERT_SYM" />
+              </node>
+              <node concept="liA8E" id="2tcGHBEvbNr" role="2OqNvi">
+                <ref role="37wK5l" to="qrld:54i3Fxd17bK" resolve="equals" />
+                <node concept="37vLTw" id="2tcGHBEvbNs" role="37wK5m">
+                  <ref role="3cqZAo" node="2tcGHBEvbMH" resolve="symbol" />
+                </node>
+              </node>
+            </node>
+            <node concept="3clFbS" id="2tcGHBEvbNt" role="3eOfB_">
+              <node concept="3cpWs6" id="2tcGHBEvhtS" role="3cqZAp">
+                <node concept="3VsKOn" id="2tcGHBEvhLT" role="3cqZAk">
+                  <ref role="3VsUkX" node="6infEALA98Q" resolve="AssertSolver" />
+                </node>
+              </node>
+              <node concept="3clFbH" id="2tcGHBEvbNB" role="3cqZAp" />
+            </node>
+          </node>
+          <node concept="3eNFk2" id="2tcGHBEvbNC" role="3eNLev">
+            <node concept="2OqwBi" id="2tcGHBEvbND" role="3eO9$A">
+              <node concept="10M0yZ" id="2tcGHBEvbNE" role="2Oq$k0">
+                <ref role="1PxDUh" to="xq5w:5$WbtTOYoMb" resolve="LogicalPredicate" />
+                <ref role="3cqZAo" to="xq5w:5uFPQ7C26$b" resolve="BOUND_SYM" />
+              </node>
+              <node concept="liA8E" id="2tcGHBEvbNF" role="2OqNvi">
+                <ref role="37wK5l" to="qrld:54i3Fxd17bK" resolve="equals" />
+                <node concept="37vLTw" id="2tcGHBEvbNG" role="37wK5m">
+                  <ref role="3cqZAo" node="2tcGHBEvbMH" resolve="symbol" />
+                </node>
+              </node>
+            </node>
+            <node concept="3clFbS" id="2tcGHBEvbNH" role="3eOfB_">
+              <node concept="3cpWs6" id="2tcGHBEviab" role="3cqZAp">
+                <node concept="3VsKOn" id="2tcGHBEviCP" role="3cqZAk">
+                  <ref role="3VsUkX" node="60B5zVEZP8W" resolve="LogicalSolver" />
+                </node>
+              </node>
+              <node concept="3clFbH" id="2tcGHBEvbNR" role="3cqZAp" />
+            </node>
+          </node>
+          <node concept="3eNFk2" id="2tcGHBEvbNS" role="3eNLev">
+            <node concept="2OqwBi" id="2tcGHBEvbNT" role="3eO9$A">
+              <node concept="10M0yZ" id="2tcGHBEvbNU" role="2Oq$k0">
+                <ref role="1PxDUh" to="xq5w:5$WbtTOYoMb" resolve="LogicalPredicate" />
+                <ref role="3cqZAo" to="xq5w:5uFPQ7C279$" resolve="FREE_SYM" />
+              </node>
+              <node concept="liA8E" id="2tcGHBEvbNV" role="2OqNvi">
+                <ref role="37wK5l" to="qrld:54i3Fxd17bK" resolve="equals" />
+                <node concept="37vLTw" id="2tcGHBEvbNW" role="37wK5m">
+                  <ref role="3cqZAo" node="2tcGHBEvbMH" resolve="symbol" />
+                </node>
+              </node>
+            </node>
+            <node concept="3clFbS" id="2tcGHBEvbNX" role="3eOfB_">
+              <node concept="3cpWs6" id="2tcGHBEviXX" role="3cqZAp">
+                <node concept="3VsKOn" id="2tcGHBEviXY" role="3cqZAk">
+                  <ref role="3VsUkX" node="60B5zVEZP8W" resolve="LogicalSolver" />
+                </node>
+              </node>
+              <node concept="3clFbH" id="2tcGHBEvbO7" role="3cqZAp" />
+            </node>
+          </node>
+          <node concept="3eNFk2" id="2tcGHBEBfnQ" role="3eNLev">
+            <node concept="2OqwBi" id="2tcGHBEBfGw" role="3eO9$A">
+              <node concept="2OqwBi" id="2tcGHBEBfAB" role="2Oq$k0">
+                <node concept="37vLTw" id="2tcGHBEBf$7" role="2Oq$k0">
+                  <ref role="3cqZAo" node="2tcGHBEvbMH" resolve="symbol" />
+                </node>
+                <node concept="liA8E" id="2tcGHBEBfDD" role="2OqNvi">
+                  <ref role="37wK5l" to="qrld:5uFPQ7B$$w_" resolve="toString" />
+                </node>
+              </node>
+              <node concept="liA8E" id="2tcGHBEBfL8" role="2OqNvi">
+                <ref role="37wK5l" to="wyt6:~String.startsWith(java.lang.String):boolean" resolve="startsWith" />
+                <node concept="Xl_RD" id="2tcGHBEBfNQ" role="37wK5m">
+                  <property role="Xl_RC" value="J:" />
+                </node>
+              </node>
+            </node>
+            <node concept="3clFbS" id="2tcGHBEBfnS" role="3eOfB_">
+              <node concept="3SKdUt" id="2tcGHBEBfVp" role="3cqZAp">
+                <node concept="3SKdUq" id="2tcGHBEBfVq" role="3SKWNk">
+                  <property role="3SKdUp" value="FIXME hack!" />
+                </node>
+              </node>
+              <node concept="3SKdUt" id="2tcGHBEBgN6" role="3cqZAp">
+                <node concept="3SKdUq" id="2tcGHBEBgN8" role="3SKWNk">
+                  <property role="3SKdUp" value="TODO: Java predicate doesn't have a solver" />
+                </node>
+              </node>
+              <node concept="3cpWs6" id="2tcGHBEBhbq" role="3cqZAp">
+                <node concept="10Nm6u" id="2tcGHBEBhxG" role="3cqZAk" />
+              </node>
+              <node concept="3clFbH" id="2tcGHBEBhHz" role="3cqZAp" />
+            </node>
+          </node>
+          <node concept="9aQIb" id="2tcGHBEvbO8" role="9aQIa">
+            <node concept="3clFbS" id="2tcGHBEvbO9" role="9aQI4">
+              <node concept="YS8fn" id="2tcGHBEvbOa" role="3cqZAp">
+                <node concept="2ShNRf" id="2tcGHBEvbOb" role="YScLw">
+                  <node concept="1pGfFk" id="2tcGHBEvbOc" role="2ShVmc">
+                    <ref role="37wK5l" to="wyt6:~IllegalArgumentException.&lt;init&gt;(java.lang.String)" resolve="IllegalArgumentException" />
+                    <node concept="3cpWs3" id="2tcGHBEvbOd" role="37wK5m">
+                      <node concept="37vLTw" id="2tcGHBEvbOe" role="3uHU7w">
+                        <ref role="3cqZAo" node="2tcGHBEvbMH" resolve="symbol" />
+                      </node>
+                      <node concept="Xl_RD" id="2tcGHBEvbOf" role="3uHU7B">
+                        <property role="Xl_RC" value="unknown symbol: " />
+                      </node>
+                    </node>
+                  </node>
+                </node>
               </node>
             </node>
           </node>
         </node>
+        <node concept="3clFbH" id="2tcGHBEvbOg" role="3cqZAp" />
+      </node>
+      <node concept="2AHcQZ" id="2tcGHBEvbOh" role="2AJF6D">
+        <ref role="2AI5Lk" to="wyt6:~Override" resolve="Override" />
       </node>
     </node>
-    <node concept="2tJIrI" id="5uFPQ7BZbUe" role="jymVt" />
-    <node concept="2tJIrI" id="7ISVfSIy3Y" role="jymVt" />
     <node concept="3Tm1VV" id="5jPBdK_$TM" role="1B3o_S" />
-    <node concept="312cEg" id="5mr7UHch7DV" role="jymVt">
-      <property role="TrG5h" value="computingSession" />
-      <node concept="3Tm6S6" id="5mr7UHch7DW" role="1B3o_S" />
-      <node concept="3uibUv" id="5mr7UHch7DY" role="1tU5fm">
-        <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="ComputingSession" />
-      </node>
-    </node>
     <node concept="2tJIrI" id="5mr7UHchpFD" role="jymVt" />
-    <node concept="312cEg" id="5mr7UHchbU9" role="jymVt">
-      <property role="TrG5h" value="computingTracer" />
-      <node concept="3Tm6S6" id="5mr7UHchbUa" role="1B3o_S" />
-      <node concept="3uibUv" id="5mr7UHchbUc" role="1tU5fm">
-        <ref role="3uigEE" to="qrld:24Vro6cQnrj" resolve="ComputingTracer" />
-      </node>
+    <node concept="3uibUv" id="2tcGHBEec09" role="1zkMxy">
+      <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="SessionSolver" />
     </node>
   </node>
 </model>
diff --git a/languages/jetbrains.mps.logic/jchr/models/jetbrains/mps/logic/jchr/program.mps b/languages/jetbrains.mps.logic/jchr/models/jetbrains/mps/logic/jchr/program.mps
index 85622ae5..3d943d7d 100644
--- a/languages/jetbrains.mps.logic/jchr/models/jetbrains/mps/logic/jchr/program.mps
+++ b/languages/jetbrains.mps.logic/jchr/models/jetbrains/mps/logic/jchr/program.mps
@@ -299,57 +299,39 @@
       </node>
       <node concept="3Tm6S6" id="7ISVfSIeUM" role="1B3o_S" />
       <node concept="3clFbS" id="7ISVfSIeJ0" role="3clF47">
-        <node concept="3cpWs8" id="7ISVfSIkA4" role="3cqZAp">
-          <node concept="3cpWsn" id="7ISVfSIkA5" role="3cpWs9">
+        <node concept="3cpWs8" id="2tcGHBEeeWq" role="3cqZAp">
+          <node concept="3cpWsn" id="2tcGHBEeeWr" role="3cpWs9">
             <property role="TrG5h" value="csession" />
-            <node concept="3uibUv" id="7ISVfSIk_R" role="1tU5fm">
-              <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="ComputingSession" />
+            <node concept="3uibUv" id="2tcGHBEeeWo" role="1tU5fm">
+              <ref role="3uigEE" to="95zw:7ISVfSIxNO" resolve="JchrSolver" />
             </node>
-            <node concept="2OqwBi" id="7ISVfSIkA6" role="33vP2m">
-              <node concept="2YIFZM" id="7ISVfSIkA7" role="2Oq$k0">
-                <ref role="37wK5l" to="qrld:6Kcfpq7BWKD" resolve="with" />
-                <ref role="1Pybhc" to="qrld:6Kcfpq7B0b0" resolve="ComputingSession" />
-                <node concept="2OqwBi" id="7ISVfSIkA8" role="37wK5m">
-                  <node concept="37vLTw" id="7ISVfSIkA9" role="2Oq$k0">
-                    <ref role="3cqZAo" node="7ISVfSIeK_" resolve="config" />
-                  </node>
-                  <node concept="2OwXpG" id="5jPBdK_kJY" role="2OqNvi">
-                    <ref role="2Oxat5" node="7ISVfSIioQ" resolve="predicateSymbols" />
-                  </node>
-                </node>
-              </node>
-              <node concept="liA8E" id="7ISVfSIkAb" role="2OqNvi">
-                <ref role="37wK5l" to="qrld:6Kcfpq7Cgrc" resolve="newSession" />
+            <node concept="2ShNRf" id="2tcGHBEeeWs" role="33vP2m">
+              <node concept="HV5vD" id="2tcGHBEiA0q" role="2ShVmc">
+                <ref role="HV5vE" to="95zw:7ISVfSIxNO" resolve="JchrSolver" />
               </node>
             </node>
           </node>
         </node>
-        <node concept="3clFbH" id="5mr7UHchezJ" role="3cqZAp" />
         <node concept="3clFbF" id="5jPBdK_B63" role="3cqZAp">
           <node concept="2OqwBi" id="5jPBdK_Bcd" role="3clFbG">
-            <node concept="2ShNRf" id="5jPBdK_BqZ" role="2Oq$k0">
-              <node concept="1pGfFk" id="5jPBdK_Br0" role="2ShVmc">
-                <ref role="37wK5l" to="95zw:5mr7UHch7og" resolve="Symbols" />
-                <node concept="37vLTw" id="5jPBdK_Br1" role="37wK5m">
-                  <ref role="3cqZAo" node="7ISVfSIkA5" resolve="csession" />
-                </node>
-                <node concept="2OqwBi" id="5jPBdK_Br2" role="37wK5m">
-                  <node concept="37vLTw" id="5jPBdK_Br3" role="2Oq$k0">
-                    <ref role="3cqZAo" node="7ISVfSIeK_" resolve="config" />
-                  </node>
-                  <node concept="2OwXpG" id="5jPBdK_Br4" role="2OqNvi">
-                    <ref role="2Oxat5" node="5mr7UHcbs2A" resolve="computingTracer" />
-                  </node>
-                </node>
-              </node>
+            <node concept="37vLTw" id="2tcGHBEeeW$" role="2Oq$k0">
+              <ref role="3cqZAo" node="2tcGHBEeeWr" resolve="csession" />
             </node>
             <node concept="liA8E" id="5jPBdK_Bhd" role="2OqNvi">
-              <ref role="37wK5l" to="95zw:5jPBdK__lx" resolve="registerSymbols" />
-              <node concept="2OqwBi" id="5jPBdK_Bie" role="37wK5m">
-                <node concept="37vLTw" id="5jPBdK_Bif" role="2Oq$k0">
+              <ref role="37wK5l" to="qrld:2tcGHBEix86" resolve="init" />
+              <node concept="2OqwBi" id="2tcGHBEeeWu" role="37wK5m">
+                <node concept="37vLTw" id="2tcGHBEeeWv" role="2Oq$k0">
                   <ref role="3cqZAo" node="7ISVfSIeK_" resolve="config" />
                 </node>
-                <node concept="2OwXpG" id="5jPBdK_Big" role="2OqNvi">
+                <node concept="2OwXpG" id="2tcGHBEeeWw" role="2OqNvi">
+                  <ref role="2Oxat5" node="5mr7UHcbs2A" resolve="computingTracer" />
+                </node>
+              </node>
+              <node concept="2OqwBi" id="2tcGHBEeeWx" role="37wK5m">
+                <node concept="37vLTw" id="2tcGHBEeeWy" role="2Oq$k0">
+                  <ref role="3cqZAo" node="7ISVfSIeK_" resolve="config" />
+                </node>
+                <node concept="2OwXpG" id="2tcGHBEeeWz" role="2OqNvi">
                   <ref role="2Oxat5" node="7ISVfSIioQ" resolve="predicateSymbols" />
                 </node>
               </node>
@@ -361,14 +343,14 @@
           <node concept="2ShNRf" id="7ISVfSIeOF" role="3clFbG">
             <node concept="1pGfFk" id="7ISVfSIeUk" role="2ShVmc">
               <ref role="37wK5l" node="7ISVfSIeTk" resolve="JchrEvaluationSession" />
-              <node concept="37vLTw" id="7ISVfSIkQC" role="37wK5m">
-                <ref role="3cqZAo" node="7ISVfSIkA5" resolve="csession" />
+              <node concept="37vLTw" id="2tcGHBEefc_" role="37wK5m">
+                <ref role="3cqZAo" node="2tcGHBEeeWr" resolve="csession" />
               </node>
               <node concept="2ShNRf" id="5mr7UHcc2yd" role="37wK5m">
                 <node concept="1pGfFk" id="5mr7UHcc2ye" role="2ShVmc">
                   <ref role="37wK5l" node="5mr7UHcaVkq" resolve="JchrHandlerLauncher" />
-                  <node concept="37vLTw" id="5mr7UHcc2yf" role="37wK5m">
-                    <ref role="3cqZAo" node="7ISVfSIkA5" resolve="csession" />
+                  <node concept="37vLTw" id="2tcGHBEeg5l" role="37wK5m">
+                    <ref role="3cqZAo" node="2tcGHBEeeWr" resolve="csession" />
                   </node>
                   <node concept="2OqwBi" id="7feMCq_ddlK" role="37wK5m">
                     <node concept="37vLTw" id="7feMCq_ddlL" role="2Oq$k0">
@@ -404,9 +386,9 @@
     <node concept="2tJIrI" id="7ISVfSIeRz" role="jymVt" />
     <node concept="3clFbW" id="7ISVfSIeTk" role="jymVt">
       <node concept="37vLTG" id="7ISVfSIkR3" role="3clF46">
-        <property role="TrG5h" value="computingSession" />
+        <property role="TrG5h" value="sessionSolver" />
         <node concept="3uibUv" id="7ISVfSIkVZ" role="1tU5fm">
-          <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="ComputingSession" />
+          <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="SessionSolver" />
         </node>
       </node>
       <node concept="37vLTG" id="5mr7UHcaZSN" role="3clF46">
@@ -423,11 +405,11 @@
             <node concept="2OqwBi" id="7ISVfSIll0" role="37vLTJ">
               <node concept="Xjq3P" id="7ISVfSIll3" role="2Oq$k0" />
               <node concept="2OwXpG" id="7ISVfSIlkZ" role="2OqNvi">
-                <ref role="2Oxat5" node="7ISVfSIlkQ" resolve="computingSession" />
+                <ref role="2Oxat5" node="7ISVfSIlkQ" resolve="sessionSolver" />
               </node>
             </node>
             <node concept="37vLTw" id="7ISVfSIll4" role="37vLTx">
-              <ref role="3cqZAo" node="7ISVfSIkR3" resolve="computingSession" />
+              <ref role="3cqZAo" node="7ISVfSIkR3" resolve="sessionSolver" />
             </node>
           </node>
         </node>
@@ -473,31 +455,17 @@
       </node>
     </node>
     <node concept="2tJIrI" id="5jPBdKD$fT" role="jymVt" />
-    <node concept="3clFb_" id="7ISVfSIXWF" role="jymVt">
-      <property role="TrG5h" value="computingTracer" />
-      <property role="1EzhhJ" value="false" />
-      <node concept="3uibUv" id="7ISVfSIXWG" role="3clF45">
-        <ref role="3uigEE" to="qrld:24Vro6cQnrj" resolve="ComputingTracer" />
-      </node>
-      <node concept="3Tm1VV" id="7ISVfSIXWH" role="1B3o_S" />
-      <node concept="3clFbS" id="7ISVfSIXWJ" role="3clF47">
-        <node concept="3clFbF" id="7ISVfSIXWL" role="3cqZAp">
-          <node concept="10Nm6u" id="7ISVfSIXWK" role="3clFbG" />
-        </node>
-      </node>
-    </node>
-    <node concept="2tJIrI" id="7ISVfSIXIO" role="jymVt" />
     <node concept="3clFb_" id="7ISVfSIg2_" role="jymVt">
-      <property role="TrG5h" value="computingSession" />
+      <property role="TrG5h" value="sessionSolver" />
       <property role="1EzhhJ" value="false" />
       <node concept="3uibUv" id="7ISVfSIg2A" role="3clF45">
-        <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="ComputingSession" />
+        <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="SessionSolver" />
       </node>
       <node concept="3Tm1VV" id="7ISVfSIg2B" role="1B3o_S" />
       <node concept="3clFbS" id="7ISVfSIg2D" role="3clF47">
         <node concept="3clFbF" id="7ISVfSIo7v" role="3cqZAp">
           <node concept="37vLTw" id="7ISVfSIo7u" role="3clFbG">
-            <ref role="3cqZAo" node="7ISVfSIlkQ" resolve="computingSession" />
+            <ref role="3cqZAo" node="7ISVfSIlkQ" resolve="sessionSolver" />
           </node>
         </node>
       </node>
@@ -1324,10 +1292,10 @@
       <ref role="3uigEE" to="rchb:5uFPQ7BvN_d" resolve="EvaluationSession" />
     </node>
     <node concept="312cEg" id="7ISVfSIlkQ" role="jymVt">
-      <property role="TrG5h" value="computingSession" />
+      <property role="TrG5h" value="sessionSolver" />
       <node concept="3Tm6S6" id="7ISVfSIlkR" role="1B3o_S" />
       <node concept="3uibUv" id="7ISVfSIlkT" role="1tU5fm">
-        <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="ComputingSession" />
+        <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="SessionSolver" />
       </node>
     </node>
     <node concept="312cEg" id="5mr7UHcbWmK" role="jymVt">
@@ -1408,7 +1376,7 @@
       <node concept="37vLTG" id="5mr7UHcaVA5" role="3clF46">
         <property role="TrG5h" value="computingSession" />
         <node concept="3uibUv" id="5mr7UHcaVA4" role="1tU5fm">
-          <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="ComputingSession" />
+          <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="SessionSolver" />
         </node>
       </node>
       <node concept="37vLTG" id="7feMCq_d4AN" role="3clF46">
@@ -1903,7 +1871,7 @@
                     <ref role="3cqZAo" node="4xBopTzsgb1" resolve="computingSession" />
                   </node>
                   <node concept="liA8E" id="4xBopTzsN2B" role="2OqNvi">
-                    <ref role="37wK5l" to="qrld:4xBopTzsxxs" resolve="lookupPredicateQueryable" />
+                    <ref role="37wK5l" to="qrld:4xBopTzsxxs" resolve="lookupQueryable" />
                     <node concept="AH0OO" id="4xBopTzsNgy" role="37wK5m">
                       <node concept="37vLTw" id="4xBopTzsNjV" role="AHEQo">
                         <ref role="3cqZAo" node="4XdxyAO7SVY" resolve="i" />
@@ -2000,7 +1968,7 @@
       <node concept="37vLTG" id="4xBopTzsgb1" role="3clF46">
         <property role="TrG5h" value="computingSession" />
         <node concept="3uibUv" id="4xBopTzsgXB" role="1tU5fm">
-          <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="ComputingSession" />
+          <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="SessionSolver" />
         </node>
       </node>
       <node concept="3uibUv" id="41ox5VndY2j" role="3clF45">
@@ -2027,7 +1995,7 @@
       <property role="TrG5h" value="computingSession" />
       <node concept="3Tm6S6" id="5mr7UHcaVDp" role="1B3o_S" />
       <node concept="3uibUv" id="5mr7UHcaVDr" role="1tU5fm">
-        <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="ComputingSession" />
+        <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="SessionSolver" />
       </node>
     </node>
     <node concept="312cEg" id="5jPBdKDvkn" role="jymVt">
diff --git a/languages/jetbrains.mps.logic/reactor/jetbrains.mps.logic.reactor.msd b/languages/jetbrains.mps.logic/reactor/jetbrains.mps.logic.reactor.msd
index 3eaefa6b..00b70ae0 100644
--- a/languages/jetbrains.mps.logic/reactor/jetbrains.mps.logic.reactor.msd
+++ b/languages/jetbrains.mps.logic/reactor/jetbrains.mps.logic.reactor.msd
@@ -9,7 +9,6 @@
   <dependencies>
     <dependency reexport="false">6354ebe7-c22a-4a0f-ac54-50b52ab9b065(JDK)</dependency>
     <dependency reexport="false">6ed54515-acc8-4d1e-a16c-9fd6cfe951ea(MPS.Core)</dependency>
-    <dependency reexport="false">7526e0cf-1ce7-46f8-a555-9eca1e06c23b(jetbrains.mps.logic.atom)</dependency>
   </dependencies>
   <languageVersions>
     <language id="f3061a53-9226-4cc5-a443-f952ceaf5816" fqName="jetbrains.mps.baseLanguage" version="4" />
@@ -23,7 +22,6 @@
     <module reference="6354ebe7-c22a-4a0f-ac54-50b52ab9b065(JDK)" version="0" />
     <module reference="6ed54515-acc8-4d1e-a16c-9fd6cfe951ea(MPS.Core)" version="0" />
     <module reference="8865b7a8-5271-43d3-884c-6fd1d9cfdd34(MPS.OpenAPI)" version="0" />
-    <module reference="7526e0cf-1ce7-46f8-a555-9eca1e06c23b(jetbrains.mps.logic.atom)" version="0" />
     <module reference="bbf5c548-7111-4a53-a117-cdefc664cf34(jetbrains.mps.logic.reactor)" version="0" />
   </dependencyVersions>
 </solution>
diff --git a/languages/jetbrains.mps.logic/reactor/models/jetbrains/mps/logic/reactor/constraint.mps b/languages/jetbrains.mps.logic/reactor/models/jetbrains/mps/logic/reactor/constraint.mps
index 30d9d38b..a0045424 100644
--- a/languages/jetbrains.mps.logic/reactor/models/jetbrains/mps/logic/reactor/constraint.mps
+++ b/languages/jetbrains.mps.logic/reactor/models/jetbrains/mps/logic/reactor/constraint.mps
@@ -43,7 +43,6 @@
       <concept id="1145552977093" name="jetbrains.mps.baseLanguage.structure.GenericNewExpression" flags="nn" index="2ShNRf">
         <child id="1145553007750" name="creator" index="2ShVmc" />
       </concept>
-      <concept id="1070462154015" name="jetbrains.mps.baseLanguage.structure.StaticFieldDeclaration" flags="ig" index="Wx3nA" />
       <concept id="1070475354124" name="jetbrains.mps.baseLanguage.structure.ThisExpression" flags="nn" index="Xjq3P" />
       <concept id="1070475587102" name="jetbrains.mps.baseLanguage.structure.SuperConstructorInvocation" flags="nn" index="XkiVB" />
       <concept id="1070475926800" name="jetbrains.mps.baseLanguage.structure.StringLiteral" flags="nn" index="Xl_RD">
@@ -69,12 +68,10 @@
       <concept id="1068390468200" name="jetbrains.mps.baseLanguage.structure.FieldDeclaration" flags="ig" index="312cEg" />
       <concept id="1068390468198" name="jetbrains.mps.baseLanguage.structure.ClassConcept" flags="ig" index="312cEu">
         <property id="1075300953594" name="abstractClass" index="1sVAO0" />
-        <property id="1221565133444" name="isFinal" index="1EXbeo" />
         <child id="1095933932569" name="implementedInterface" index="EKbjA" />
         <child id="1165602531693" name="superclass" index="1zkMxy" />
       </concept>
       <concept id="1068431474542" name="jetbrains.mps.baseLanguage.structure.VariableDeclaration" flags="ng" index="33uBYm">
-        <property id="1176718929932" name="isFinal" index="3TUv4t" />
         <child id="1068431790190" name="initializer" index="33vP2m" />
       </concept>
       <concept id="1092119917967" name="jetbrains.mps.baseLanguage.structure.MulExpression" flags="nn" index="17qRlL" />
@@ -88,6 +85,7 @@
         <child id="5680397130376446158" name="type" index="1tU5fm" />
       </concept>
       <concept id="1068580123132" name="jetbrains.mps.baseLanguage.structure.BaseMethodDeclaration" flags="ng" index="3clF44">
+        <property id="4276006055363816570" name="isSynchronized" index="od$2w" />
         <property id="1181808852946" name="isFinal" index="DiZV1" />
         <child id="1068580123133" name="returnType" index="3clF45" />
         <child id="1068580123134" name="parameter" index="3clF46" />
@@ -176,12 +174,6 @@
         <child id="1163668934364" name="ifFalse" index="3K4GZi" />
       </concept>
       <concept id="1208890769693" name="jetbrains.mps.baseLanguage.structure.ArrayLengthOperation" flags="nn" index="1Rwk04" />
-      <concept id="6329021646629104957" name="jetbrains.mps.baseLanguage.structure.TextCommentPart" flags="nn" index="3SKdUq">
-        <property id="6329021646629104958" name="text" index="3SKdUp" />
-      </concept>
-      <concept id="6329021646629104954" name="jetbrains.mps.baseLanguage.structure.SingleLineComment" flags="nn" index="3SKdUt">
-        <child id="6329021646629175155" name="commentPart" index="3SKWNk" />
-      </concept>
       <concept id="1146644602865" name="jetbrains.mps.baseLanguage.structure.PublicVisibility" flags="nn" index="3Tm1VV" />
       <concept id="1146644623116" name="jetbrains.mps.baseLanguage.structure.PrivateVisibility" flags="nn" index="3Tm6S6" />
       <concept id="1146644641414" name="jetbrains.mps.baseLanguage.structure.ProtectedVisibility" flags="nn" index="3Tmbuc" />
@@ -258,7 +250,6 @@
       <node concept="3Tm1VV" id="6Kcfpq7AYIz" role="1B3o_S" />
       <node concept="3clFbS" id="6Kcfpq7AYI$" role="3clF47" />
     </node>
-    <node concept="2tJIrI" id="5uFPQ7C2w0z" role="jymVt" />
     <node concept="2tJIrI" id="6Kcfpq7AYPU" role="jymVt" />
     <node concept="3Tm1VV" id="6Kcfpq7AYBi" role="1B3o_S" />
     <node concept="3uibUv" id="6Kcfpq7AZqN" role="3HQHJm">
@@ -266,184 +257,75 @@
     </node>
   </node>
   <node concept="312cEu" id="6Kcfpq7B0b0">
-    <property role="TrG5h" value="ComputingSession" />
-    <node concept="2tJIrI" id="6Kcfpq7B0Qi" role="jymVt" />
-    <node concept="2YIFZL" id="6Kcfpq7BWKD" role="jymVt">
-      <property role="TrG5h" value="with" />
-      <node concept="37vLTG" id="6Kcfpq7BX5n" role="3clF46">
+    <property role="TrG5h" value="SessionSolver" />
+    <property role="1sVAO0" value="true" />
+    <node concept="2tJIrI" id="2tcGHBEencT" role="jymVt" />
+    <node concept="3clFb_" id="2tcGHBEeol1" role="jymVt">
+      <property role="1EzhhJ" value="false" />
+      <property role="TrG5h" value="init" />
+      <property role="od$2w" value="false" />
+      <property role="DiZV1" value="false" />
+      <property role="2aFKle" value="false" />
+      <node concept="37vLTG" id="2tcGHBEirFR" role="3clF46">
         <property role="TrG5h" value="predicateSymbols" />
-        <node concept="8X2XB" id="6Kcfpq7BX92" role="1tU5fm">
-          <node concept="3uibUv" id="5uFPQ7C2cwz" role="8Xvag">
+        <node concept="8X2XB" id="2tcGHBEirFS" role="1tU5fm">
+          <node concept="3uibUv" id="2tcGHBEirFT" role="8Xvag">
             <ref role="3uigEE" node="5uFPQ7B$$3f" resolve="PredicateSymbol" />
           </node>
         </node>
       </node>
-      <node concept="3uibUv" id="6Kcfpq7BWZe" role="3clF45">
-        <ref role="3uigEE" node="6Kcfpq7BTQb" resolve="ComputingSession.Builder" />
-      </node>
-      <node concept="3Tm1VV" id="6Kcfpq7BWKG" role="1B3o_S" />
-      <node concept="3clFbS" id="6Kcfpq7BWKH" role="3clF47">
-        <node concept="3clFbF" id="6Kcfpq7BYpl" role="3cqZAp">
-          <node concept="2ShNRf" id="6Kcfpq7BYpj" role="3clFbG">
-            <node concept="1pGfFk" id="6Kcfpq7BZmp" role="2ShVmc">
-              <ref role="37wK5l" node="6Kcfpq7BWZz" resolve="ComputingSession.Builder" />
-              <node concept="37vLTw" id="6Kcfpq7BZmK" role="37wK5m">
-                <ref role="3cqZAo" node="6Kcfpq7BX5n" resolve="predicateSymbols" />
-              </node>
+      <node concept="3clFbS" id="2tcGHBEeol4" role="3clF47">
+        <node concept="3clFbF" id="2tcGHBEepha" role="3cqZAp">
+          <node concept="1rXfSq" id="2tcGHBEeph9" role="3clFbG">
+            <ref role="37wK5l" node="5jPBdK__lx" resolve="registerSymbols" />
+            <node concept="10Nm6u" id="2tcGHBEiyk2" role="37wK5m" />
+            <node concept="37vLTw" id="2tcGHBEisqb" role="37wK5m">
+              <ref role="3cqZAo" node="2tcGHBEirFR" resolve="predicateSymbols" />
             </node>
           </node>
         </node>
       </node>
+      <node concept="3Tm1VV" id="2tcGHBEenL5" role="1B3o_S" />
+      <node concept="3cqZAl" id="2tcGHBEeoTR" role="3clF45" />
     </node>
-    <node concept="2tJIrI" id="6Kcfpq7BY0I" role="jymVt" />
-    <node concept="3clFbW" id="6Kcfpq7BJaF" role="jymVt">
-      <node concept="37vLTG" id="24Vro6cQB61" role="3clF46">
-        <property role="TrG5h" value="tracer" />
-        <node concept="3uibUv" id="24Vro6cQBin" role="1tU5fm">
+    <node concept="2tJIrI" id="2tcGHBEix_v" role="jymVt" />
+    <node concept="3clFb_" id="2tcGHBEix86" role="jymVt">
+      <property role="1EzhhJ" value="false" />
+      <property role="TrG5h" value="init" />
+      <property role="od$2w" value="false" />
+      <property role="DiZV1" value="false" />
+      <property role="2aFKle" value="false" />
+      <node concept="37vLTG" id="2tcGHBEix87" role="3clF46">
+        <property role="TrG5h" value="computingTracer" />
+        <node concept="3uibUv" id="2tcGHBEix88" role="1tU5fm">
           <ref role="3uigEE" node="24Vro6cQnrj" resolve="ComputingTracer" />
         </node>
       </node>
-      <node concept="3cqZAl" id="6Kcfpq7BJaH" role="3clF45" />
-      <node concept="3Tm6S6" id="6Kcfpq7CfrR" role="1B3o_S" />
-      <node concept="3clFbS" id="6Kcfpq7BJaJ" role="3clF47">
-        <node concept="3clFbF" id="24Vro6cQBEg" role="3cqZAp">
-          <node concept="37vLTI" id="24Vro6cQBHr" role="3clFbG">
-            <node concept="37vLTw" id="24Vro6cQBIm" role="37vLTx">
-              <ref role="3cqZAo" node="24Vro6cQB61" resolve="tracer" />
-            </node>
-            <node concept="2OqwBi" id="24Vro6cQBEw" role="37vLTJ">
-              <node concept="Xjq3P" id="24Vro6cQBEf" role="2Oq$k0" />
-              <node concept="2OwXpG" id="24Vro6cQBGy" role="2OqNvi">
-                <ref role="2Oxat5" node="24Vro6cQyK4" resolve="tracer" />
-              </node>
-            </node>
-          </node>
-        </node>
-      </node>
-    </node>
-    <node concept="2tJIrI" id="6Kcfpq7Bmmj" role="jymVt" />
-    <node concept="312cEu" id="6Kcfpq7BTQb" role="jymVt">
-      <property role="2bfB8j" value="false" />
-      <property role="1sVAO0" value="false" />
-      <property role="1EXbeo" value="false" />
-      <property role="TrG5h" value="Builder" />
-      <node concept="2tJIrI" id="6Kcfpq7BU6k" role="jymVt" />
-      <node concept="3clFbW" id="6Kcfpq7BWZz" role="jymVt">
-        <node concept="37vLTG" id="6Kcfpq7BXbe" role="3clF46">
-          <property role="TrG5h" value="symbols" />
-          <node concept="8X2XB" id="6Kcfpq7BXeT" role="1tU5fm">
-            <node concept="3uibUv" id="5uFPQ7C2d7R" role="8Xvag">
-              <ref role="3uigEE" node="5uFPQ7B$$3f" resolve="PredicateSymbol" />
-            </node>
-          </node>
-        </node>
-        <node concept="3cqZAl" id="6Kcfpq7BWZ_" role="3clF45" />
-        <node concept="3clFbS" id="6Kcfpq7BWZA" role="3clF47">
-          <node concept="3clFbF" id="5uFPQ7C2ilB" role="3cqZAp">
-            <node concept="2OqwBi" id="5uFPQ7C2izF" role="3clFbG">
-              <node concept="2OqwBi" id="5uFPQ7C2ipx" role="2Oq$k0">
-                <node concept="Xjq3P" id="5uFPQ7C2il_" role="2Oq$k0" />
-                <node concept="2OwXpG" id="5uFPQ7C2iv2" role="2OqNvi">
-                  <ref role="2Oxat5" node="6Kcfpq7C1nA" resolve="predicateSymbols" />
-                </node>
-              </node>
-              <node concept="liA8E" id="5uFPQ7C2iMT" role="2OqNvi">
-                <ref role="37wK5l" to="33ny:~List.addAll(java.util.Collection):boolean" resolve="addAll" />
-                <node concept="2YIFZM" id="5uFPQ7C2iQ4" role="37wK5m">
-                  <ref role="37wK5l" to="33ny:~Arrays.asList(java.lang.Object...):java.util.List" resolve="asList" />
-                  <ref role="1Pybhc" to="33ny:~Arrays" resolve="Arrays" />
-                  <node concept="37vLTw" id="5uFPQ7C2iQ5" role="37wK5m">
-                    <ref role="3cqZAo" node="6Kcfpq7BXbe" resolve="symbols" />
-                  </node>
-                </node>
-              </node>
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-          </node>
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-        <node concept="3Tm6S6" id="6Kcfpq7BWZN" role="1B3o_S" />
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-      <node concept="2tJIrI" id="6Kcfpq7BU6m" role="jymVt" />
-      <node concept="3clFb_" id="24Vro6cQjzH" role="jymVt">
-        <property role="TrG5h" value="withTracer" />
-        <node concept="37vLTG" id="24Vro6cQl7h" role="3clF46">
-          <property role="TrG5h" value="tracer" />
-          <node concept="3uibUv" id="24Vro6cQoAS" role="1tU5fm">
-            <ref role="3uigEE" node="24Vro6cQnrj" resolve="ComputingTracer" />
-          </node>
-        </node>
-        <node concept="3uibUv" id="24Vro6cQk4j" role="3clF45">
-          <ref role="3uigEE" node="6Kcfpq7BTQb" resolve="ComputingSession.Builder" />
-        </node>
-        <node concept="3Tm1VV" id="24Vro6cQjzK" role="1B3o_S" />
-        <node concept="3clFbS" id="24Vro6cQjzL" role="3clF47">
-          <node concept="3clFbF" id="24Vro6cQoBu" role="3cqZAp">
-            <node concept="37vLTI" id="24Vro6cQoBw" role="3clFbG">
-              <node concept="2OqwBi" id="24Vro6cQoB$" role="37vLTJ">
-                <node concept="Xjq3P" id="24Vro6cQoBB" role="2Oq$k0" />
-                <node concept="2OwXpG" id="24Vro6cQoBz" role="2OqNvi">
-                  <ref role="2Oxat5" node="24Vro6cQoBq" resolve="tracer" />
-                </node>
-              </node>
-              <node concept="37vLTw" id="24Vro6cQoBC" role="37vLTx">
-                <ref role="3cqZAo" node="24Vro6cQl7h" resolve="tracer" />
-              </node>
-            </node>
-          </node>
-          <node concept="3clFbF" id="24Vro6cQpEB" role="3cqZAp">
-            <node concept="Xjq3P" id="24Vro6cQpE_" role="3clFbG" />
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-      <node concept="3clFb_" id="6Kcfpq7Cgrc" role="jymVt">
-        <property role="TrG5h" value="newSession" />
-        <node concept="3uibUv" id="6Kcfpq7CgVs" role="3clF45">
-          <ref role="3uigEE" node="6Kcfpq7B0b0" resolve="ComputingSession" />
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-        <node concept="3clFbS" id="6Kcfpq7Cgrf" role="3clF47">
-          <node concept="3cpWs6" id="6Kcfpq7Crdz" role="3cqZAp">
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-              <node concept="1pGfFk" id="7ISVfSJaEp" role="2ShVmc">
-                <ref role="37wK5l" node="6Kcfpq7BJaF" resolve="ComputingSession" />
-                <node concept="37vLTw" id="7ISVfSJaEq" role="37wK5m">
-                  <ref role="3cqZAo" node="24Vro6cQoBq" resolve="tracer" />
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-          </node>
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-        <node concept="3Tm1VV" id="6Kcfpq7CgII" role="1B3o_S" />
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-      <node concept="2tJIrI" id="6Kcfpq7Cg9v" role="jymVt" />
-      <node concept="312cEg" id="6Kcfpq7C1nA" role="jymVt">
+      <node concept="37vLTG" id="2tcGHBEix89" role="3clF46">
         <property role="TrG5h" value="predicateSymbols" />
-        <node concept="3Tm6S6" id="6Kcfpq7C1nB" role="1B3o_S" />
-        <node concept="3uibUv" id="6Kcfpq7C1q$" role="1tU5fm">
-          <ref role="3uigEE" to="33ny:~List" resolve="List" />
-          <node concept="3uibUv" id="5uFPQ7C2djU" role="11_B2D">
+        <node concept="8X2XB" id="2tcGHBEix8a" role="1tU5fm">
+          <node concept="3uibUv" id="2tcGHBEix8b" role="8Xvag">
             <ref role="3uigEE" node="5uFPQ7B$$3f" resolve="PredicateSymbol" />
           </node>
         </node>
-        <node concept="2ShNRf" id="6Kcfpq7C1rR" role="33vP2m">
-          <node concept="1pGfFk" id="6Kcfpq7C1wG" role="2ShVmc">
-            <ref role="37wK5l" to="33ny:~ArrayList.&lt;init&gt;()" resolve="ArrayList" />
-            <node concept="3uibUv" id="5uFPQ7C2eqF" role="1pMfVU">
-              <ref role="3uigEE" node="5uFPQ7B$$3f" resolve="PredicateSymbol" />
+      </node>
+      <node concept="3clFbS" id="2tcGHBEix8c" role="3clF47">
+        <node concept="3clFbF" id="2tcGHBEix8d" role="3cqZAp">
+          <node concept="1rXfSq" id="2tcGHBEix8e" role="3clFbG">
+            <ref role="37wK5l" node="5jPBdK__lx" resolve="registerSymbols" />
+            <node concept="37vLTw" id="2tcGHBEix8f" role="37wK5m">
+              <ref role="3cqZAo" node="2tcGHBEix87" resolve="computingTracer" />
+            </node>
+            <node concept="37vLTw" id="2tcGHBEix8g" role="37wK5m">
+              <ref role="3cqZAo" node="2tcGHBEix89" resolve="predicateSymbols" />
             </node>
           </node>
         </node>
       </node>
-      <node concept="3Tm1VV" id="4xBopTzuEuZ" role="1B3o_S" />
-      <node concept="312cEg" id="24Vro6cQoBq" role="jymVt">
-        <property role="TrG5h" value="tracer" />
-        <node concept="3Tm6S6" id="24Vro6cQoBr" role="1B3o_S" />
-        <node concept="3uibUv" id="24Vro6cQoBt" role="1tU5fm">
-          <ref role="3uigEE" node="24Vro6cQnrj" resolve="ComputingTracer" />
-        </node>
-      </node>
+      <node concept="3Tm1VV" id="2tcGHBEix8h" role="1B3o_S" />
+      <node concept="3cqZAl" id="2tcGHBEix8i" role="3clF45" />
     </node>
-    <node concept="2tJIrI" id="6Kcfpq7BSVl" role="jymVt" />
-    <node concept="2tJIrI" id="24Vro6cQmg2" role="jymVt" />
+    <node concept="2tJIrI" id="2tcGHBEe33n" role="jymVt" />
     <node concept="3clFb_" id="4xBopTznHV5" role="jymVt">
       <property role="TrG5h" value="ask" />
       <node concept="37vLTG" id="4xBopTznJFk" role="3clF46">
@@ -463,55 +345,13 @@
       <node concept="10P_77" id="4xBopTznJ7k" role="3clF45" />
       <node concept="3Tm1VV" id="4xBopTznHV8" role="1B3o_S" />
       <node concept="3clFbS" id="4xBopTznHV9" role="3clF47">
-        <node concept="3cpWs8" id="4xBopTznKPC" role="3cqZAp">
-          <node concept="3cpWsn" id="4xBopTznKPD" role="3cpWs9">
-            <property role="TrG5h" value="solver" />
-            <node concept="3uibUv" id="4xBopTznKP_" role="1tU5fm">
-              <ref role="3uigEE" node="6Kcfpq7AYBh" resolve="Queryable" />
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-            <node concept="1rXfSq" id="4xBopTznKPE" role="33vP2m">
-              <ref role="37wK5l" node="6Kcfpq7B10O" resolve="solver" />
-              <node concept="37vLTw" id="4xBopTznKPF" role="37wK5m">
-                <ref role="3cqZAo" node="4xBopTznJFk" resolve="predicateSymbol" />
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-        <node concept="3clFbJ" id="4xBopTznKRc" role="3cqZAp">
-          <node concept="3clFbS" id="4xBopTznKRe" role="3clFbx">
-            <node concept="YS8fn" id="2GO7tyJTJIH" role="3cqZAp">
-              <node concept="2ShNRf" id="2GO7tyJTJJ5" role="YScLw">
-                <node concept="1pGfFk" id="2GO7tyJTJXR" role="2ShVmc">
-                  <ref role="37wK5l" to="wyt6:~IllegalStateException.&lt;init&gt;(java.lang.String)" resolve="IllegalStateException" />
-                  <node concept="3cpWs3" id="2GO7tyJTLcI" role="37wK5m">
-                    <node concept="Xl_RD" id="2GO7tyJTLcT" role="3uHU7w">
-                      <property role="Xl_RC" value="'" />
-                    </node>
-                    <node concept="3cpWs3" id="2GO7tyJTK_t" role="3uHU7B">
-                      <node concept="Xl_RD" id="2GO7tyJTJZp" role="3uHU7B">
-                        <property role="Xl_RC" value="no solver for '" />
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-                      <node concept="37vLTw" id="4xBopTznLdt" role="3uHU7w">
-                        <ref role="3cqZAo" node="4xBopTznJFk" resolve="predicateSymbol" />
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-                    </node>
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-          <node concept="3clFbC" id="4xBopTznL4F" role="3clFbw">
-            <node concept="10Nm6u" id="4xBopTznL58" role="3uHU7w" />
-            <node concept="37vLTw" id="4xBopTznKYd" role="3uHU7B">
-              <ref role="3cqZAo" node="4xBopTznKPD" resolve="solver" />
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-          </node>
-        </node>
-        <node concept="3clFbH" id="4xBopTznM87" role="3cqZAp" />
         <node concept="3cpWs6" id="4xBopTznMkq" role="3cqZAp">
           <node concept="2OqwBi" id="4xBopTznNyu" role="3cqZAk">
-            <node concept="37vLTw" id="4xBopTznN7k" role="2Oq$k0">
-              <ref role="3cqZAo" node="4xBopTznKPD" resolve="solver" />
+            <node concept="1rXfSq" id="2tcGHBEe1CZ" role="2Oq$k0">
+              <ref role="37wK5l" node="6Kcfpq7B10O" resolve="solver" />
+              <node concept="37vLTw" id="2tcGHBEe1D0" role="37wK5m">
+                <ref role="3cqZAo" node="4xBopTznJFk" resolve="predicateSymbol" />
+              </node>
             </node>
             <node concept="liA8E" id="4xBopTznNUP" role="2OqNvi">
               <ref role="37wK5l" node="6Kcfpq7AYIw" resolve="ask" />
@@ -525,6 +365,9 @@
           </node>
         </node>
       </node>
+      <node concept="2AHcQZ" id="2tcGHBE69cd" role="2AJF6D">
+        <ref role="2AI5Lk" to="wyt6:~Override" resolve="Override" />
+      </node>
     </node>
     <node concept="2tJIrI" id="4xBopTznHuj" role="jymVt" />
     <node concept="3clFb_" id="4xBopTznPKO" role="jymVt">
@@ -532,55 +375,13 @@
       <node concept="3cqZAl" id="4xBopTznPKQ" role="3clF45" />
       <node concept="3Tm1VV" id="4xBopTznPKR" role="1B3o_S" />
       <node concept="3clFbS" id="4xBopTznPKS" role="3clF47">
-        <node concept="3cpWs8" id="4xBopTznRC7" role="3cqZAp">
-          <node concept="3cpWsn" id="4xBopTznRC8" role="3cpWs9">
-            <property role="TrG5h" value="handler" />
-            <node concept="3uibUv" id="4xBopTznRC6" role="1tU5fm">
-              <ref role="3uigEE" node="6Kcfpq7AXVG" resolve="Instructible" />
-            </node>
-            <node concept="1rXfSq" id="4xBopTznRC9" role="33vP2m">
-              <ref role="37wK5l" node="6Kcfpq7B0QC" resolve="handler" />
-              <node concept="37vLTw" id="4xBopTznRCa" role="37wK5m">
-                <ref role="3cqZAo" node="4xBopTznQGo" resolve="symbol" />
-              </node>
-            </node>
-          </node>
-        </node>
-        <node concept="3clFbJ" id="4xBopTznRD$" role="3cqZAp">
-          <node concept="3clFbS" id="4xBopTznRDA" role="3clFbx">
-            <node concept="YS8fn" id="4xBopTznRO3" role="3cqZAp">
-              <node concept="2ShNRf" id="4xBopTznRO4" role="YScLw">
-                <node concept="1pGfFk" id="4xBopTznRO5" role="2ShVmc">
-                  <ref role="37wK5l" to="wyt6:~IllegalStateException.&lt;init&gt;(java.lang.String)" resolve="IllegalStateException" />
-                  <node concept="3cpWs3" id="4xBopTznRO6" role="37wK5m">
-                    <node concept="Xl_RD" id="4xBopTznRO7" role="3uHU7w">
-                      <property role="Xl_RC" value="'" />
-                    </node>
-                    <node concept="3cpWs3" id="4xBopTznRO8" role="3uHU7B">
-                      <node concept="Xl_RD" id="4xBopTznRO9" role="3uHU7B">
-                        <property role="Xl_RC" value="no handler for '" />
-                      </node>
-                      <node concept="37vLTw" id="4xBopTznRVo" role="3uHU7w">
-                        <ref role="3cqZAo" node="4xBopTznQGo" resolve="symbol" />
-                      </node>
-                    </node>
-                  </node>
-                </node>
-              </node>
-            </node>
-          </node>
-          <node concept="3clFbC" id="4xBopTznRNl" role="3clFbw">
-            <node concept="10Nm6u" id="4xBopTznRNK" role="3uHU7w" />
-            <node concept="37vLTw" id="4xBopTznRKo" role="3uHU7B">
-              <ref role="3cqZAo" node="4xBopTznRC8" resolve="handler" />
-            </node>
-          </node>
-        </node>
-        <node concept="3clFbH" id="4xBopTznS8w" role="3cqZAp" />
         <node concept="3clFbF" id="4xBopTznSgM" role="3cqZAp">
           <node concept="2OqwBi" id="4xBopTznSmj" role="3clFbG">
-            <node concept="37vLTw" id="4xBopTznSgK" role="2Oq$k0">
-              <ref role="3cqZAo" node="4xBopTznRC8" resolve="handler" />
+            <node concept="1rXfSq" id="2tcGHBEe2sb" role="2Oq$k0">
+              <ref role="37wK5l" node="6Kcfpq7B0QC" resolve="handler" />
+              <node concept="37vLTw" id="2tcGHBEe2sc" role="37wK5m">
+                <ref role="3cqZAo" node="4xBopTznQGo" resolve="symbol" />
+              </node>
             </node>
             <node concept="liA8E" id="4xBopTznSrf" role="2OqNvi">
               <ref role="37wK5l" node="6Kcfpq7AY2Z" resolve="tell" />
@@ -608,11 +409,13 @@
           </node>
         </node>
       </node>
+      <node concept="2AHcQZ" id="2tcGHBE69_a" role="2AJF6D">
+        <ref role="2AI5Lk" to="wyt6:~Override" resolve="Override" />
+      </node>
     </node>
-    <node concept="2tJIrI" id="4xBopTznH1y" role="jymVt" />
-    <node concept="2tJIrI" id="4xBopTzsya7" role="jymVt" />
+    <node concept="2tJIrI" id="2tcGHBEqIuN" role="jymVt" />
     <node concept="3clFb_" id="4xBopTzsxxs" role="jymVt">
-      <property role="TrG5h" value="lookupPredicateQueryable" />
+      <property role="TrG5h" value="lookupQueryable" />
       <node concept="37vLTG" id="4xBopTzsxxt" role="3clF46">
         <property role="TrG5h" value="clazz" />
         <node concept="3uibUv" id="4xBopTzsxxu" role="1tU5fm">
@@ -695,6 +498,89 @@
         </node>
       </node>
     </node>
+    <node concept="2tJIrI" id="2tcGHBEveN9" role="jymVt" />
+    <node concept="3clFb_" id="2tcGHBEqJAf" role="jymVt">
+      <property role="1EzhhJ" value="true" />
+      <property role="TrG5h" value="solverClass" />
+      <property role="od$2w" value="false" />
+      <property role="DiZV1" value="false" />
+      <property role="2aFKle" value="false" />
+      <node concept="3clFbS" id="2tcGHBEqJAi" role="3clF47" />
+      <node concept="3Tm1VV" id="2tcGHBEqJbr" role="1B3o_S" />
+      <node concept="3uibUv" id="2tcGHBEqJz1" role="3clF45">
+        <ref role="3uigEE" to="wyt6:~Class" resolve="Class" />
+        <node concept="3qUE_q" id="2tcGHBEqJ$x" role="11_B2D">
+          <node concept="3uibUv" id="2tcGHBEqJ$D" role="3qUE_r">
+            <ref role="3uigEE" node="6Kcfpq7AYBh" resolve="Queryable" />
+          </node>
+        </node>
+      </node>
+      <node concept="37vLTG" id="2tcGHBEqJZo" role="3clF46">
+        <property role="TrG5h" value="predicateSymbol" />
+        <node concept="3uibUv" id="2tcGHBEqJZn" role="1tU5fm">
+          <ref role="3uigEE" node="5uFPQ7B$$3f" resolve="PredicateSymbol" />
+        </node>
+      </node>
+    </node>
+    <node concept="2tJIrI" id="6Kcfpq7BSVl" role="jymVt" />
+    <node concept="3clFb_" id="2tcGHBEehCv" role="jymVt">
+      <property role="1EzhhJ" value="true" />
+      <property role="TrG5h" value="registerSymbol" />
+      <property role="od$2w" value="false" />
+      <property role="DiZV1" value="false" />
+      <property role="2aFKle" value="false" />
+      <node concept="3clFbS" id="2tcGHBEehCy" role="3clF47" />
+      <node concept="3Tmbuc" id="2tcGHBEeh8H" role="1B3o_S" />
+      <node concept="3cqZAl" id="2tcGHBEehCt" role="3clF45" />
+      <node concept="37vLTG" id="2tcGHBEeico" role="3clF46">
+        <property role="TrG5h" value="predicateSymbol" />
+        <node concept="3uibUv" id="2tcGHBEeicn" role="1tU5fm">
+          <ref role="3uigEE" node="5uFPQ7B$$3f" resolve="PredicateSymbol" />
+        </node>
+      </node>
+      <node concept="37vLTG" id="2tcGHBEivC2" role="3clF46">
+        <property role="TrG5h" value="computingTracer" />
+        <node concept="3uibUv" id="2tcGHBEivRX" role="1tU5fm">
+          <ref role="3uigEE" node="24Vro6cQnrj" resolve="ComputingTracer" />
+        </node>
+      </node>
+    </node>
+    <node concept="2tJIrI" id="2tcGHBEeg_v" role="jymVt" />
+    <node concept="3clFb_" id="6Kcfpq7B2LV" role="jymVt">
+      <property role="TrG5h" value="registerSolver" />
+      <node concept="3cqZAl" id="6Kcfpq7B2LW" role="3clF45" />
+      <node concept="3Tmbuc" id="2tcGHBEe5yG" role="1B3o_S" />
+      <node concept="3clFbS" id="6Kcfpq7B2LY" role="3clF47">
+        <node concept="3clFbF" id="6Kcfpq7BcIe" role="3cqZAp">
+          <node concept="2OqwBi" id="6Kcfpq7BcN$" role="3clFbG">
+            <node concept="37vLTw" id="6Kcfpq7BcId" role="2Oq$k0">
+              <ref role="3cqZAo" node="6Kcfpq7B51L" resolve="solvers" />
+            </node>
+            <node concept="liA8E" id="6Kcfpq7BcWr" role="2OqNvi">
+              <ref role="37wK5l" to="33ny:~Map.put(java.lang.Object,java.lang.Object):java.lang.Object" resolve="put" />
+              <node concept="37vLTw" id="6Kcfpq7Bd4J" role="37wK5m">
+                <ref role="3cqZAo" node="6Kcfpq7B2LZ" resolve="constraint" />
+              </node>
+              <node concept="37vLTw" id="6Kcfpq7Bdi0" role="37wK5m">
+                <ref role="3cqZAo" node="6Kcfpq7B2M1" resolve="queryable" />
+              </node>
+            </node>
+          </node>
+        </node>
+      </node>
+      <node concept="37vLTG" id="6Kcfpq7B2LZ" role="3clF46">
+        <property role="TrG5h" value="constraint" />
+        <node concept="3uibUv" id="5uFPQ7C2Fvo" role="1tU5fm">
+          <ref role="3uigEE" node="5uFPQ7B$$3f" resolve="PredicateSymbol" />
+        </node>
+      </node>
+      <node concept="37vLTG" id="6Kcfpq7B2M1" role="3clF46">
+        <property role="TrG5h" value="queryable" />
+        <node concept="3uibUv" id="6Kcfpq7B2R9" role="1tU5fm">
+          <ref role="3uigEE" node="6Kcfpq7AYBh" resolve="Queryable" />
+        </node>
+      </node>
+    </node>
     <node concept="2tJIrI" id="4xBopTzsrrI" role="jymVt" />
     <node concept="3clFb_" id="6Kcfpq7B0QC" role="jymVt">
       <property role="TrG5h" value="handler" />
@@ -707,48 +593,16 @@
       <node concept="3uibUv" id="6Kcfpq7B0SD" role="3clF45">
         <ref role="3uigEE" node="6Kcfpq7AXVG" resolve="Instructible" />
       </node>
-      <node concept="3Tmbuc" id="6Kcfpq7Bmcu" role="1B3o_S" />
+      <node concept="3Tm6S6" id="2tcGHBEa2YX" role="1B3o_S" />
       <node concept="3clFbS" id="6Kcfpq7B0QG" role="3clF47">
-        <node concept="3clFbJ" id="6Kcfpq7B7yk" role="3cqZAp">
-          <node concept="3clFbS" id="6Kcfpq7B7yl" role="3clFbx">
-            <node concept="YS8fn" id="6Kcfpq7B83r" role="3cqZAp">
-              <node concept="2ShNRf" id="6Kcfpq7B83J" role="YScLw">
-                <node concept="1pGfFk" id="6Kcfpq7B8cz" role="2ShVmc">
-                  <ref role="37wK5l" to="wyt6:~IllegalStateException.&lt;init&gt;(java.lang.String)" resolve="IllegalStateException" />
-                  <node concept="3cpWs3" id="6Kcfpq7B8lK" role="37wK5m">
-                    <node concept="37vLTw" id="6Kcfpq7B8n0" role="3uHU7w">
-                      <ref role="3cqZAo" node="6Kcfpq7B0U_" resolve="symbol" />
-                    </node>
-                    <node concept="Xl_RD" id="6Kcfpq7B8cZ" role="3uHU7B">
-                      <property role="Xl_RC" value="no handler: " />
-                    </node>
-                  </node>
-                </node>
+        <node concept="3clFbF" id="2tcGHBEe0QC" role="3cqZAp">
+          <node concept="1rXfSq" id="2tcGHBEe0QB" role="3clFbG">
+            <ref role="37wK5l" node="6Kcfpq7B10O" resolve="solver" />
+            <node concept="10QFUN" id="2tcGHBEe0UA" role="37wK5m">
+              <node concept="3uibUv" id="2tcGHBEe0U$" role="10QFUM">
+                <ref role="3uigEE" node="5uFPQ7B$$3f" resolve="PredicateSymbol" />
               </node>
-            </node>
-          </node>
-          <node concept="3fqX7Q" id="6Kcfpq7B7yE" role="3clFbw">
-            <node concept="2OqwBi" id="6Kcfpq7B7GQ" role="3fr31v">
-              <node concept="37vLTw" id="6Kcfpq7B7$Z" role="2Oq$k0">
-                <ref role="3cqZAo" node="2GO7tyJTzV1" resolve="handlers" />
-              </node>
-              <node concept="liA8E" id="6Kcfpq7B7VP" role="2OqNvi">
-                <ref role="37wK5l" to="33ny:~Map.containsKey(java.lang.Object):boolean" resolve="containsKey" />
-                <node concept="37vLTw" id="6Kcfpq7B7Z$" role="37wK5m">
-                  <ref role="3cqZAo" node="6Kcfpq7B0U_" resolve="symbol" />
-                </node>
-              </node>
-            </node>
-          </node>
-        </node>
-        <node concept="3clFbF" id="6Kcfpq7B9Fo" role="3cqZAp">
-          <node concept="2OqwBi" id="6Kcfpq7B9Me" role="3clFbG">
-            <node concept="37vLTw" id="6Kcfpq7B9Fm" role="2Oq$k0">
-              <ref role="3cqZAo" node="2GO7tyJTzV1" resolve="handlers" />
-            </node>
-            <node concept="liA8E" id="6Kcfpq7Ba26" role="2OqNvi">
-              <ref role="37wK5l" to="33ny:~Map.get(java.lang.Object):java.lang.Object" resolve="get" />
-              <node concept="37vLTw" id="6Kcfpq7Ba5I" role="37wK5m">
+              <node concept="37vLTw" id="2tcGHBEe0U_" role="10QFUP">
                 <ref role="3cqZAo" node="6Kcfpq7B0U_" resolve="symbol" />
               </node>
             </node>
@@ -757,6 +611,52 @@
       </node>
     </node>
     <node concept="2tJIrI" id="6Kcfpq7B13i" role="jymVt" />
+    <node concept="3clFb_" id="5jPBdK__lx" role="jymVt">
+      <property role="TrG5h" value="registerSymbols" />
+      <node concept="37vLTG" id="2tcGHBEisq_" role="3clF46">
+        <property role="TrG5h" value="computingTracer" />
+        <node concept="3uibUv" id="2tcGHBEisqA" role="1tU5fm">
+          <ref role="3uigEE" node="24Vro6cQnrj" resolve="ComputingTracer" />
+        </node>
+      </node>
+      <node concept="37vLTG" id="2tcGHBEisqB" role="3clF46">
+        <property role="TrG5h" value="predicateSymbols" />
+        <node concept="8X2XB" id="2tcGHBEisqC" role="1tU5fm">
+          <node concept="3uibUv" id="2tcGHBEisqD" role="8Xvag">
+            <ref role="3uigEE" node="5uFPQ7B$$3f" resolve="PredicateSymbol" />
+          </node>
+        </node>
+      </node>
+      <node concept="3cqZAl" id="5jPBdK__lz" role="3clF45" />
+      <node concept="3Tm6S6" id="2tcGHBEemsp" role="1B3o_S" />
+      <node concept="3clFbS" id="5jPBdK__l_" role="3clF47">
+        <node concept="1DcWWT" id="5mr7UHchfPx" role="3cqZAp">
+          <node concept="3clFbS" id="5mr7UHchfPz" role="2LFqv$">
+            <node concept="3clFbF" id="5jPBdK_AI8" role="3cqZAp">
+              <node concept="1rXfSq" id="5jPBdK_AI6" role="3clFbG">
+                <ref role="37wK5l" node="2tcGHBEehCv" resolve="registerSymbol" />
+                <node concept="37vLTw" id="5jPBdK_AJz" role="37wK5m">
+                  <ref role="3cqZAo" node="5mr7UHchfP_" resolve="symbol" />
+                </node>
+                <node concept="37vLTw" id="2tcGHBEivX_" role="37wK5m">
+                  <ref role="3cqZAo" node="2tcGHBEisq_" resolve="computingTracer" />
+                </node>
+              </node>
+            </node>
+          </node>
+          <node concept="3cpWsn" id="5mr7UHchfP_" role="1Duv9x">
+            <property role="TrG5h" value="symbol" />
+            <node concept="3uibUv" id="5mr7UHchfPD" role="1tU5fm">
+              <ref role="3uigEE" node="5uFPQ7B$$3f" resolve="PredicateSymbol" />
+            </node>
+          </node>
+          <node concept="37vLTw" id="2tcGHBEisKZ" role="1DdaDG">
+            <ref role="3cqZAo" node="2tcGHBEisqB" resolve="predicateSymbols" />
+          </node>
+        </node>
+      </node>
+    </node>
+    <node concept="2tJIrI" id="2tcGHBEeaCY" role="jymVt" />
     <node concept="3clFb_" id="6Kcfpq7B10O" role="jymVt">
       <property role="TrG5h" value="solver" />
       <node concept="37vLTG" id="6Kcfpq7B10P" role="3clF46">
@@ -768,7 +668,7 @@
       <node concept="3uibUv" id="6Kcfpq7B13G" role="3clF45">
         <ref role="3uigEE" node="6Kcfpq7AYBh" resolve="Queryable" />
       </node>
-      <node concept="3Tmbuc" id="6Kcfpq7Bm4i" role="1B3o_S" />
+      <node concept="3Tm6S6" id="2tcGHBEa3qD" role="1B3o_S" />
       <node concept="3clFbS" id="6Kcfpq7B10T" role="3clF47">
         <node concept="3clFbJ" id="6Kcfpq7BaRr" role="3cqZAp">
           <node concept="3clFbS" id="6Kcfpq7BaRs" role="3clFbx">
@@ -818,124 +718,6 @@
       </node>
     </node>
     <node concept="2tJIrI" id="6Kcfpq7B2xY" role="jymVt" />
-    <node concept="3clFb_" id="6Kcfpq7B2yH" role="jymVt">
-      <property role="TrG5h" value="registerHandler" />
-      <node concept="3cqZAl" id="6Kcfpq7B2yJ" role="3clF45" />
-      <node concept="3Tm1VV" id="7ISVfSIN_0" role="1B3o_S" />
-      <node concept="3clFbS" id="6Kcfpq7B2yL" role="3clF47">
-        <node concept="3clFbF" id="6Kcfpq7Bc9w" role="3cqZAp">
-          <node concept="2OqwBi" id="6Kcfpq7BceQ" role="3clFbG">
-            <node concept="37vLTw" id="6Kcfpq7Bc9v" role="2Oq$k0">
-              <ref role="3cqZAo" node="2GO7tyJTzV1" resolve="handlers" />
-            </node>
-            <node concept="liA8E" id="6Kcfpq7BcnH" role="2OqNvi">
-              <ref role="37wK5l" to="33ny:~Map.put(java.lang.Object,java.lang.Object):java.lang.Object" resolve="put" />
-              <node concept="37vLTw" id="6Kcfpq7Bcu$" role="37wK5m">
-                <ref role="3cqZAo" node="6Kcfpq7B2G3" resolve="symbol" />
-              </node>
-              <node concept="37vLTw" id="6Kcfpq7BcBF" role="37wK5m">
-                <ref role="3cqZAo" node="6Kcfpq7B2I6" resolve="instructible" />
-              </node>
-            </node>
-          </node>
-        </node>
-      </node>
-      <node concept="37vLTG" id="6Kcfpq7B2G3" role="3clF46">
-        <property role="TrG5h" value="symbol" />
-        <node concept="3uibUv" id="5uFPQ7Cdvbz" role="1tU5fm">
-          <ref role="3uigEE" node="5uFPQ7B$mzX" resolve="Symbol" />
-        </node>
-      </node>
-      <node concept="37vLTG" id="6Kcfpq7B2I6" role="3clF46">
-        <property role="TrG5h" value="instructible" />
-        <node concept="3uibUv" id="6Kcfpq7B2K1" role="1tU5fm">
-          <ref role="3uigEE" node="6Kcfpq7AXVG" resolve="Instructible" />
-        </node>
-      </node>
-    </node>
-    <node concept="2tJIrI" id="6Kcfpq7BlwP" role="jymVt" />
-    <node concept="3clFb_" id="6Kcfpq7B2LV" role="jymVt">
-      <property role="TrG5h" value="registerSolver" />
-      <node concept="3cqZAl" id="6Kcfpq7B2LW" role="3clF45" />
-      <node concept="3Tm1VV" id="7ISVfSIO0L" role="1B3o_S" />
-      <node concept="3clFbS" id="6Kcfpq7B2LY" role="3clF47">
-        <node concept="3clFbF" id="6Kcfpq7BcIe" role="3cqZAp">
-          <node concept="2OqwBi" id="6Kcfpq7BcN$" role="3clFbG">
-            <node concept="37vLTw" id="6Kcfpq7BcId" role="2Oq$k0">
-              <ref role="3cqZAo" node="6Kcfpq7B51L" resolve="solvers" />
-            </node>
-            <node concept="liA8E" id="6Kcfpq7BcWr" role="2OqNvi">
-              <ref role="37wK5l" to="33ny:~Map.put(java.lang.Object,java.lang.Object):java.lang.Object" resolve="put" />
-              <node concept="37vLTw" id="6Kcfpq7Bd4J" role="37wK5m">
-                <ref role="3cqZAo" node="6Kcfpq7B2LZ" resolve="constraint" />
-              </node>
-              <node concept="37vLTw" id="6Kcfpq7Bdi0" role="37wK5m">
-                <ref role="3cqZAo" node="6Kcfpq7B2M1" resolve="queryable" />
-              </node>
-            </node>
-          </node>
-        </node>
-        <node concept="3SKdUt" id="5jPBdK_GNG" role="3cqZAp">
-          <node concept="3SKdUq" id="5jPBdK_GNI" role="3SKWNk">
-            <property role="3SKdUp" value="TODO: must we keep them twice?" />
-          </node>
-        </node>
-        <node concept="3clFbF" id="5jPBdK_Gux" role="3cqZAp">
-          <node concept="2OqwBi" id="5jPBdK_Guy" role="3clFbG">
-            <node concept="37vLTw" id="5jPBdK_Guz" role="2Oq$k0">
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-      <node concept="37vLTG" id="6Kcfpq7B2M1" role="3clF46">
-        <property role="TrG5h" value="queryable" />
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-          <ref role="3uigEE" node="6Kcfpq7AYBh" resolve="Queryable" />
-        </node>
-      </node>
-    </node>
-    <node concept="2tJIrI" id="6Kcfpq7B5YO" role="jymVt" />
-    <node concept="312cEg" id="2GO7tyJTzV1" role="jymVt">
-      <property role="TrG5h" value="handlers" />
-      <node concept="3Tm6S6" id="2GO7tyJTzV2" role="1B3o_S" />
-      <node concept="3uibUv" id="2GO7tyJT$59" role="1tU5fm">
-        <ref role="3uigEE" to="33ny:~Map" resolve="Map" />
-        <node concept="3uibUv" id="5uFPQ7CdwdJ" role="11_B2D">
-          <ref role="3uigEE" node="5uFPQ7B$mzX" resolve="Symbol" />
-        </node>
-        <node concept="3uibUv" id="6Kcfpq7B59z" role="11_B2D">
-          <ref role="3uigEE" node="6Kcfpq7AXVG" resolve="Instructible" />
-        </node>
-      </node>
-      <node concept="2ShNRf" id="2GO7tyJTFoC" role="33vP2m">
-        <node concept="1pGfFk" id="2GO7tyJTFM0" role="2ShVmc">
-          <ref role="37wK5l" to="33ny:~HashMap.&lt;init&gt;()" resolve="HashMap" />
-          <node concept="3uibUv" id="5uFPQ7CdwpF" role="1pMfVU">
-            <ref role="3uigEE" node="5uFPQ7B$mzX" resolve="Symbol" />
-          </node>
-          <node concept="3uibUv" id="6Kcfpq7B5is" role="1pMfVU">
-            <ref role="3uigEE" node="6Kcfpq7AXVG" resolve="Instructible" />
-          </node>
-        </node>
-      </node>
-    </node>
-    <node concept="2tJIrI" id="6Kcfpq7B5zv" role="jymVt" />
     <node concept="312cEg" id="6Kcfpq7B51L" role="jymVt">
       <property role="TrG5h" value="solvers" />
       <node concept="3Tm6S6" id="6Kcfpq7B51M" role="1B3o_S" />
@@ -960,22 +742,19 @@
         </node>
       </node>
     </node>
-    <node concept="2tJIrI" id="6Kcfpq7B4NQ" role="jymVt" />
     <node concept="3Tm1VV" id="6Kcfpq7B0b1" role="1B3o_S" />
     <node concept="3UR2Jj" id="6Kcfpq7CBOa" role="lGtFl">
       <node concept="TZ5HA" id="6Kcfpq7CBOb" role="TZ5H$">
         <node concept="1dT_AC" id="6Kcfpq7CBOc" role="1dT_Ay">
-          <property role="1dT_AB" value="Computing session is used to provide an interface for handlers and solvers working together in a single session." />
+          <property role="1dT_AB" value="Is used to provide an interface for handlers and solvers working together in a single session." />
         </node>
       </node>
     </node>
-    <node concept="312cEg" id="24Vro6cQyK4" role="jymVt">
-      <property role="TrG5h" value="tracer" />
-      <property role="3TUv4t" value="true" />
-      <node concept="3Tm6S6" id="24Vro6cQyK5" role="1B3o_S" />
-      <node concept="3uibUv" id="24Vro6cQyK7" role="1tU5fm">
-        <ref role="3uigEE" node="24Vro6cQnrj" resolve="ComputingTracer" />
-      </node>
+    <node concept="3uibUv" id="2tcGHBE67_N" role="EKbjA">
+      <ref role="3uigEE" node="6Kcfpq7AXVG" resolve="Instructible" />
+    </node>
+    <node concept="3uibUv" id="2tcGHBE68Cy" role="EKbjA">
+      <ref role="3uigEE" node="6Kcfpq7AYBh" resolve="Queryable" />
     </node>
   </node>
   <node concept="312cEu" id="6Kcfpq7B0Wu">
@@ -1011,35 +790,6 @@
     </node>
     <node concept="2tJIrI" id="6Kcfpq7B1eT" role="jymVt" />
     <node concept="3Tm1VV" id="6Kcfpq7B0Wv" role="1B3o_S" />
-    <node concept="3clFb_" id="6Kcfpq7Bx2u" role="jymVt">
-      <property role="TrG5h" value="handler" />
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-        <property role="TrG5h" value="session" />
-        <node concept="3uibUv" id="6Kcfpq7BPpt" role="1tU5fm">
-          <ref role="3uigEE" node="6Kcfpq7B0b0" resolve="ComputingSession" />
-        </node>
-      </node>
-      <node concept="3Tm1VV" id="6Kcfpq7BxF7" role="1B3o_S" />
-      <node concept="3clFbS" id="6Kcfpq7Bx2y" role="3clF47">
-        <node concept="3clFbF" id="6Kcfpq7Byca" role="3cqZAp">
-          <node concept="2OqwBi" id="6Kcfpq7BycB" role="3clFbG">
-            <node concept="37vLTw" id="6Kcfpq7BMAJ" role="2Oq$k0">
-              <ref role="3cqZAo" node="6Kcfpq7BxYR" resolve="session" />
-            </node>
-            <node concept="liA8E" id="6Kcfpq7Bydh" role="2OqNvi">
-              <ref role="37wK5l" node="6Kcfpq7B0QC" resolve="handler" />
-              <node concept="1rXfSq" id="5uFPQ7ClHad" role="37wK5m">
-                <ref role="37wK5l" node="6Kcfpq7Bjgi" resolve="symbol" />
-              </node>
-            </node>
-          </node>
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-      </node>
-      <node concept="3uibUv" id="6Kcfpq7Bxy9" role="3clF45">
-        <ref role="3uigEE" node="6Kcfpq7AXVG" resolve="Instructible" />
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-    </node>
-    <node concept="2tJIrI" id="6Kcfpq7Bytl" role="jymVt" />
     <node concept="3clFb_" id="5uFPQ7BZhBG" role="jymVt">
       <property role="1EzhhJ" value="false" />
       <property role="TrG5h" value="arguments" />
@@ -1340,95 +1090,6 @@
       </node>
     </node>
     <node concept="2tJIrI" id="6Kcfpq7B3IY" role="jymVt" />
-    <node concept="2tJIrI" id="6Kcfpq7Cvdp" role="jymVt" />
-    <node concept="3clFb_" id="6Kcfpq7Bs88" role="jymVt">
-      <property role="TrG5h" value="registerHandler" />
-      <node concept="37vLTG" id="6Kcfpq7BtCA" role="3clF46">
-        <property role="TrG5h" value="session" />
-        <node concept="3uibUv" id="6Kcfpq7BtMO" role="1tU5fm">
-          <ref role="3uigEE" node="6Kcfpq7B0b0" resolve="ComputingSession" />
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-      </node>
-      <node concept="37vLTG" id="6Kcfpq7BtOW" role="3clF46">
-        <property role="TrG5h" value="instructible" />
-        <node concept="3uibUv" id="6Kcfpq7BtZc" role="1tU5fm">
-          <ref role="3uigEE" node="6Kcfpq7AXVG" resolve="Instructible" />
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-      <node concept="3cqZAl" id="6Kcfpq7Bs8a" role="3clF45" />
-      <node concept="3Tmbuc" id="6Kcfpq7BskN" role="1B3o_S" />
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-        <node concept="3clFbF" id="6Kcfpq7Bu1B" role="3cqZAp">
-          <node concept="2OqwBi" id="6Kcfpq7Bu22" role="3clFbG">
-            <node concept="37vLTw" id="6Kcfpq7Bu1A" role="2Oq$k0">
-              <ref role="3cqZAo" node="6Kcfpq7BtCA" resolve="session" />
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-            <node concept="liA8E" id="6Kcfpq7Bu2G" role="2OqNvi">
-              <ref role="37wK5l" node="6Kcfpq7B2yH" resolve="registerHandler" />
-              <node concept="1rXfSq" id="5uFPQ7ClHjA" role="37wK5m">
-                <ref role="37wK5l" node="6Kcfpq7Bjgi" resolve="symbol" />
-              </node>
-              <node concept="37vLTw" id="6Kcfpq7Bu3W" role="37wK5m">
-                <ref role="3cqZAo" node="6Kcfpq7BtOW" resolve="instructible" />
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-    <node concept="3clFb_" id="6Kcfpq7Buzk" role="jymVt">
-      <property role="TrG5h" value="registerSolver" />
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-        <property role="TrG5h" value="session" />
-        <node concept="3uibUv" id="6Kcfpq7Buzm" role="1tU5fm">
-          <ref role="3uigEE" node="6Kcfpq7B0b0" resolve="ComputingSession" />
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-      <node concept="37vLTG" id="6Kcfpq7Buzn" role="3clF46">
-        <property role="TrG5h" value="queryable" />
-        <node concept="3uibUv" id="6Kcfpq7Bw2C" role="1tU5fm">
-          <ref role="3uigEE" node="6Kcfpq7AYBh" resolve="Queryable" />
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-      <node concept="3cqZAl" id="6Kcfpq7Buzp" role="3clF45" />
-      <node concept="3Tmbuc" id="6Kcfpq7Buzq" role="1B3o_S" />
-      <node concept="3clFbS" id="6Kcfpq7Buzr" role="3clF47">
-        <node concept="3clFbF" id="6Kcfpq7Buzs" role="3cqZAp">
-          <node concept="2OqwBi" id="6Kcfpq7Buzt" role="3clFbG">
-            <node concept="37vLTw" id="6Kcfpq7Buzu" role="2Oq$k0">
-              <ref role="3cqZAo" node="6Kcfpq7Buzl" resolve="session" />
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-            <node concept="liA8E" id="6Kcfpq7Buzv" role="2OqNvi">
-              <ref role="37wK5l" node="6Kcfpq7B2LV" resolve="registerSolver" />
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-                <ref role="37wK5l" node="6Kcfpq7Bjgi" resolve="symbol" />
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-              <node concept="37vLTw" id="6Kcfpq7Buzx" role="37wK5m">
-                <ref role="3cqZAo" node="6Kcfpq7Buzn" resolve="queryable" />
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-        <node concept="3clFbF" id="4xBopTzylBh" role="3cqZAp">
-          <node concept="2OqwBi" id="4xBopTzylBi" role="3clFbG">
-            <node concept="37vLTw" id="4xBopTzylBj" role="2Oq$k0">
-              <ref role="3cqZAo" node="6Kcfpq7Buzl" resolve="session" />
-            </node>
-            <node concept="liA8E" id="4xBopTzylBk" role="2OqNvi">
-              <ref role="37wK5l" node="6Kcfpq7B2yH" resolve="registerHandler" />
-              <node concept="1rXfSq" id="5uFPQ7ClHsW" role="37wK5m">
-                <ref role="37wK5l" node="6Kcfpq7Bjgi" resolve="symbol" />
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-              <node concept="37vLTw" id="4xBopTzylH0" role="37wK5m">
-                <ref role="3cqZAo" node="6Kcfpq7Buzn" resolve="queryable" />
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-          </node>
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-    <node concept="2tJIrI" id="5uFPQ7C2_Hq" role="jymVt" />
     <node concept="3uibUv" id="5uFPQ7BZiil" role="EKbjA">
       <ref role="3uigEE" node="6Kcfpq7Bj7q" resolve="Predicate" />
     </node>
@@ -1444,38 +1105,7 @@
   </node>
   <node concept="3HP615" id="6Kcfpq7BfEn">
     <property role="TrG5h" value="Constraint" />
-    <node concept="2tJIrI" id="6Kcfpq7BfGc" role="jymVt" />
-    <node concept="3clFb_" id="6Kcfpq7Bg6m" role="jymVt">
-      <property role="1EzhhJ" value="true" />
-      <property role="TrG5h" value="handler" />
-      <node concept="37vLTG" id="6Kcfpq7BgaC" role="3clF46">
-        <property role="TrG5h" value="session" />
-        <node concept="3uibUv" id="6Kcfpq7BPkF" role="1tU5fm">
-          <ref role="3uigEE" node="6Kcfpq7B0b0" resolve="ComputingSession" />
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-      <node concept="3uibUv" id="6Kcfpq7Bg8G" role="3clF45">
-        <ref role="3uigEE" node="6Kcfpq7AXVG" resolve="Instructible" />
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-      <node concept="3Tm1VV" id="6Kcfpq7Bg6p" role="1B3o_S" />
-      <node concept="3clFbS" id="6Kcfpq7Bg6q" role="3clF47" />
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-    <node concept="3clFb_" id="4xBopTzlOq0" role="jymVt">
-      <property role="1EzhhJ" value="true" />
-      <property role="TrG5h" value="handlerClass" />
-      <node concept="3uibUv" id="4xBopTzlOqK" role="3clF45">
-        <ref role="3uigEE" to="wyt6:~Class" resolve="Class" />
-        <node concept="3qUE_q" id="4xBopTzlOqU" role="11_B2D">
-          <node concept="3uibUv" id="4xBopTzlOr0" role="3qUE_r">
-            <ref role="3uigEE" node="6Kcfpq7AXVG" resolve="Instructible" />
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-      <node concept="3Tm1VV" id="4xBopTzlOq3" role="1B3o_S" />
-      <node concept="3clFbS" id="4xBopTzlOq4" role="3clF47" />
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-    <node concept="2tJIrI" id="4xBopTzlOps" role="jymVt" />
     <node concept="3clFb_" id="5uFPQ7B_aTC" role="jymVt">
       <property role="1EzhhJ" value="true" />
       <property role="TrG5h" value="symbol" />
@@ -1524,21 +1154,6 @@
   </node>
   <node concept="3HP615" id="6Kcfpq7Bj7q">
     <property role="TrG5h" value="Predicate" />
-    <node concept="2tJIrI" id="6Kcfpq7Bj9f" role="jymVt" />
-    <node concept="3clFb_" id="4xBopTzlOsG" role="jymVt">
-      <property role="1EzhhJ" value="true" />
-      <property role="TrG5h" value="solverClass" />
-      <node concept="3uibUv" id="4xBopTzlOts" role="3clF45">
-        <ref role="3uigEE" to="wyt6:~Class" resolve="Class" />
-        <node concept="3qUE_q" id="4xBopTzlOtB" role="11_B2D">
-          <node concept="3uibUv" id="4xBopTzlOtH" role="3qUE_r">
-            <ref role="3uigEE" node="6Kcfpq7AYBh" resolve="Queryable" />
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-      <node concept="3Tm1VV" id="4xBopTzlOsJ" role="1B3o_S" />
-      <node concept="3clFbS" id="4xBopTzlOsK" role="3clF47" />
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     <node concept="3clFb_" id="6Kcfpq7Bjgi" role="jymVt">
       <property role="1EzhhJ" value="true" />
@@ -1723,111 +1338,6 @@
       <ref role="3uigEE" node="5uFPQ7B$mzX" resolve="Symbol" />
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-  <node concept="312cEu" id="30XHGaP1u0m">
-    <property role="TrG5h" value="StandardBuiltinConstraint" />
-    <node concept="2tJIrI" id="30XHGaP1u5g" role="jymVt" />
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-      <property role="TrG5h" value="UNIFICATION" />
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-      <node concept="3Tm1VV" id="2DKqMqO$zFX" role="1B3o_S" />
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-        </node>
-      </node>
-    </node>
-    <node concept="2tJIrI" id="30XHGaP1A8X" role="jymVt" />
-    <node concept="Wx3nA" id="54i3FxcZO14" role="jymVt">
-      <property role="TrG5h" value="BOUND" />
-      <property role="3TUv4t" value="true" />
-      <node concept="3Tm1VV" id="54i3FxcZP2q" role="1B3o_S" />
-      <node concept="3uibUv" id="5uFPQ7BM2nv" role="1tU5fm">
-        <ref role="3uigEE" node="5uFPQ7B$$3f" resolve="PredicateSymbol" />
-      </node>
-      <node concept="2ShNRf" id="5uFPQ7C8AUD" role="33vP2m">
-        <node concept="1pGfFk" id="5uFPQ7C8AUE" role="2ShVmc">
-          <ref role="37wK5l" node="5uFPQ7B$$fT" resolve="PredicateSymbol" />
-          <node concept="Xl_RD" id="5uFPQ7C8AUF" role="37wK5m">
-            <property role="Xl_RC" value="isNonVar" />
-          </node>
-          <node concept="3cmrfG" id="5uFPQ7C8AUG" role="37wK5m">
-            <property role="3cmrfH" value="1" />
-          </node>
-        </node>
-      </node>
-    </node>
-    <node concept="2tJIrI" id="30XHGaP1u5l" role="jymVt" />
-    <node concept="3Tm1VV" id="30XHGaP1u0n" role="1B3o_S" />
-  </node>
   <node concept="312cEu" id="5uFPQ7B$mzX">
     <property role="TrG5h" value="Symbol" />
     <property role="1sVAO0" value="true" />
@@ -2392,67 +1902,6 @@
       </node>
     </node>
     <node concept="2tJIrI" id="5uFPQ7BZto4" role="jymVt" />
-    <node concept="3clFb_" id="5uFPQ7BZsCn" role="jymVt">
-      <property role="1EzhhJ" value="false" />
-      <property role="TrG5h" value="handler" />
-      <node concept="37vLTG" id="5uFPQ7BZsCo" role="3clF46">
-        <property role="TrG5h" value="session" />
-        <node concept="3uibUv" id="5uFPQ7BZsCp" role="1tU5fm">
-          <ref role="3uigEE" node="6Kcfpq7B0b0" resolve="ComputingSession" />
-        </node>
-      </node>
-      <node concept="3uibUv" id="5uFPQ7BZsCq" role="3clF45">
-        <ref role="3uigEE" node="6Kcfpq7AXVG" resolve="Instructible" />
-      </node>
-      <node concept="3Tm1VV" id="5uFPQ7BZsCr" role="1B3o_S" />
-      <node concept="3clFbS" id="5uFPQ7BZsCt" role="3clF47">
-        <node concept="3clFbF" id="5uFPQ7BZupI" role="3cqZAp">
-          <node concept="2OqwBi" id="5uFPQ7BZupJ" role="3clFbG">
-            <node concept="37vLTw" id="5uFPQ7BZupK" role="2Oq$k0">
-              <ref role="3cqZAo" node="5uFPQ7BZsCo" resolve="session" />
-            </node>
-            <node concept="liA8E" id="5uFPQ7BZupL" role="2OqNvi">
-              <ref role="37wK5l" node="6Kcfpq7B0QC" resolve="handler" />
-              <node concept="1rXfSq" id="5uFPQ7ClGQi" role="37wK5m">
-                <ref role="37wK5l" node="5uFPQ7BZsCD" resolve="symbol" />
-              </node>
-            </node>
-          </node>
-        </node>
-      </node>
-    </node>
-    <node concept="2tJIrI" id="5uFPQ7CfOEd" role="jymVt" />
-    <node concept="3clFb_" id="5uFPQ7BZsCw" role="jymVt">
-      <property role="1EzhhJ" value="false" />
-      <property role="TrG5h" value="handlerClass" />
-      <node concept="3uibUv" id="5uFPQ7BZsCx" role="3clF45">
-        <ref role="3uigEE" to="wyt6:~Class" resolve="Class" />
-        <node concept="3qUE_q" id="5uFPQ7BZsCy" role="11_B2D">
-          <node concept="3uibUv" id="5uFPQ7BZsCz" role="3qUE_r">
-            <ref role="3uigEE" node="6Kcfpq7AXVG" resolve="Instructible" />
-          </node>
-        </node>
-      </node>
-      <node concept="3Tm1VV" id="5uFPQ7BZsC$" role="1B3o_S" />
-      <node concept="3clFbS" id="5uFPQ7BZsCA" role="3clF47">
-        <node concept="3SKdUt" id="5uFPQ7BZxuS" role="3cqZAp">
-          <node concept="3SKdUq" id="5uFPQ7BZxuT" role="3SKWNk">
-            <property role="3SKdUp" value="FIXME: implement me" />
-          </node>
-        </node>
-        <node concept="YS8fn" id="5uFPQ7BZxuU" role="3cqZAp">
-          <node concept="2ShNRf" id="5uFPQ7BZxuV" role="YScLw">
-            <node concept="1pGfFk" id="5uFPQ7BZxuW" role="2ShVmc">
-              <ref role="37wK5l" to="wyt6:~UnsupportedOperationException.&lt;init&gt;(java.lang.String)" resolve="UnsupportedOperationException" />
-              <node concept="Xl_RD" id="5uFPQ7BZxuX" role="37wK5m">
-                <property role="Xl_RC" value="not implemented" />
-              </node>
-            </node>
-          </node>
-        </node>
-      </node>
-    </node>
-    <node concept="2tJIrI" id="5uFPQ7BZv8C" role="jymVt" />
     <node concept="3clFb_" id="5uFPQ7BZsCD" role="jymVt">
       <property role="1EzhhJ" value="false" />
       <property role="TrG5h" value="symbol" />
diff --git a/languages/jetbrains.mps.logic/reactor/models/jetbrains/mps/logic/reactor/program.mps b/languages/jetbrains.mps.logic/reactor/models/jetbrains/mps/logic/reactor/program.mps
index fffa6d02..527bb6b2 100644
--- a/languages/jetbrains.mps.logic/reactor/models/jetbrains/mps/logic/reactor/program.mps
+++ b/languages/jetbrains.mps.logic/reactor/models/jetbrains/mps/logic/reactor/program.mps
@@ -2,8 +2,8 @@
 <model ref="r:f43ee4a0-488a-425a-87a0-594ab3b0d15f(jetbrains.mps.logic.reactor.program)">
   <persistence version="9" />
   <languages>
-    <use id="f2801650-65d5-424e-bb1b-463a8781b786" name="jetbrains.mps.baseLanguage.javadoc" version="2" />
-    <use id="f3061a53-9226-4cc5-a443-f952ceaf5816" name="jetbrains.mps.baseLanguage" version="4" />
+    <use id="f2801650-65d5-424e-bb1b-463a8781b786" name="jetbrains.mps.baseLanguage.javadoc" version="-1" />
+    <use id="f3061a53-9226-4cc5-a443-f952ceaf5816" name="jetbrains.mps.baseLanguage" version="-1" />
   </languages>
   <imports>
     <import index="qrld" ref="r:2a79c8aa-e372-4c00-8d71-5d7f3db517e4(jetbrains.mps.logic.reactor.constraint)" />
@@ -136,6 +136,12 @@
         <property role="TrG5h" value="name" />
         <node concept="17QB3L" id="78CwJJcTF59" role="1tU5fm" />
       </node>
+      <node concept="37vLTG" id="2tcGHBEqEU6" role="3clF46">
+        <property role="TrG5h" value="sessionSolver" />
+        <node concept="3uibUv" id="2tcGHBEqEVG" role="1tU5fm">
+          <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="SessionSolver" />
+        </node>
+      </node>
       <node concept="3clFbS" id="5uFPQ7BvQKl" role="3clF47">
         <node concept="3clFbJ" id="78CwJJd1N85" role="3cqZAp">
           <node concept="3clFbS" id="78CwJJd1N87" role="3clFbx">
@@ -167,6 +173,9 @@
               <node concept="37vLTw" id="78CwJJd24bb" role="37wK5m">
                 <ref role="3cqZAo" node="78CwJJcTF4u" resolve="name" />
               </node>
+              <node concept="37vLTw" id="2tcGHBEqEYH" role="37wK5m">
+                <ref role="3cqZAo" node="2tcGHBEqEU6" resolve="sessionSolver" />
+              </node>
             </node>
           </node>
         </node>
@@ -281,6 +290,28 @@
         <ref role="3uigEE" to="i8dg:7Oc59RS$wKP" resolve="InvalidRuleException" />
       </node>
     </node>
+    <node concept="2tJIrI" id="2tcGHBDZ69W" role="jymVt" />
+    <node concept="3clFb_" id="2tcGHBDZ65V" role="jymVt">
+      <property role="TrG5h" value="addRules" />
+      <property role="1EzhhJ" value="true" />
+      <node concept="37vLTG" id="2tcGHBDZ65W" role="3clF46">
+        <property role="TrG5h" value="rules" />
+        <node concept="3uibUv" id="2tcGHBDZ6et" role="1tU5fm">
+          <ref role="3uigEE" to="33ny:~Collection" resolve="Collection" />
+          <node concept="3qUE_q" id="2tcGHBDZ6gN" role="11_B2D">
+            <node concept="3uibUv" id="2tcGHBDZ6hQ" role="3qUE_r">
+              <ref role="3uigEE" to="i8dg:7eGEHDlc$9y" resolve="Rule" />
+            </node>
+          </node>
+        </node>
+      </node>
+      <node concept="3cqZAl" id="2tcGHBDZ65Y" role="3clF45" />
+      <node concept="3Tm1VV" id="2tcGHBDZ65Z" role="1B3o_S" />
+      <node concept="3clFbS" id="2tcGHBDZ660" role="3clF47" />
+      <node concept="3uibUv" id="2tcGHBDZ661" role="Sfmx6">
+        <ref role="3uigEE" to="i8dg:7Oc59RS$wKP" resolve="InvalidRuleException" />
+      </node>
+    </node>
     <node concept="2tJIrI" id="78CwJJcOot9" role="jymVt" />
     <node concept="2YIFZL" id="78CwJJd1Sv0" role="jymVt">
       <property role="TrG5h" value="setFactory" />
@@ -381,6 +412,12 @@
           <property role="TrG5h" value="name" />
           <node concept="17QB3L" id="78CwJJd248i" role="1tU5fm" />
         </node>
+        <node concept="37vLTG" id="2tcGHBEqEZe" role="3clF46">
+          <property role="TrG5h" value="sessionSolver" />
+          <node concept="3uibUv" id="2tcGHBEqF0Q" role="1tU5fm">
+            <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="SessionSolver" />
+          </node>
+        </node>
         <node concept="3uibUv" id="78CwJJd1Nnf" role="3clF45">
           <ref role="3uigEE" node="5uFPQ7BvNzE" resolve="PlanningSession" />
         </node>
@@ -554,22 +591,12 @@
       </node>
       <node concept="3Tm1VV" id="5uFPQ7Bwt90" role="1B3o_S" />
     </node>
-    <node concept="2tJIrI" id="5uFPQ7Bwwl1" role="jymVt" />
-    <node concept="3clFb_" id="7ISVfSIWX_" role="jymVt">
-      <property role="TrG5h" value="computingTracer" />
-      <property role="1EzhhJ" value="true" />
-      <node concept="3uibUv" id="7ISVfSIXiR" role="3clF45">
-        <ref role="3uigEE" to="qrld:24Vro6cQnrj" resolve="ComputingTracer" />
-      </node>
-      <node concept="3Tm1VV" id="7ISVfSIWXC" role="1B3o_S" />
-      <node concept="3clFbS" id="7ISVfSIWXD" role="3clF47" />
-    </node>
     <node concept="2tJIrI" id="7ISVfSIWE1" role="jymVt" />
     <node concept="3clFb_" id="5uFPQ7ClOzA" role="jymVt">
-      <property role="TrG5h" value="computingSession" />
+      <property role="TrG5h" value="sessionSolver" />
       <property role="1EzhhJ" value="true" />
       <node concept="3uibUv" id="5uFPQ7ClOB7" role="3clF45">
-        <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="ComputingSession" />
+        <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="SessionSolver" />
       </node>
       <node concept="3Tm1VV" id="5uFPQ7ClOzD" role="1B3o_S" />
       <node concept="3clFbS" id="5uFPQ7ClOzE" role="3clF47" />
@@ -620,33 +647,6 @@
       <node concept="3clFbS" id="5mr7UHccvdM" role="3clF47" />
     </node>
     <node concept="2tJIrI" id="5uFPQ7BZbRm" role="jymVt" />
-    <node concept="3HP615" id="5uFPQ7BwtoR" role="jymVt">
-      <property role="2bfB8j" value="true" />
-      <property role="TrG5h" value="Backend" />
-      <node concept="2tJIrI" id="5uFPQ7Bwtqx" role="jymVt" />
-      <node concept="3clFb_" id="5uFPQ7BwtvO" role="jymVt">
-        <property role="1EzhhJ" value="true" />
-        <property role="TrG5h" value="current" />
-        <node concept="3uibUv" id="5uFPQ7BwtwM" role="3clF45">
-          <ref role="3uigEE" node="5uFPQ7BvN_d" resolve="EvaluationSession" />
-        </node>
-        <node concept="3Tm1VV" id="5uFPQ7BwtvR" role="1B3o_S" />
-        <node concept="3clFbS" id="5uFPQ7BwtvS" role="3clF47" />
-      </node>
-      <node concept="2tJIrI" id="5uFPQ7Bwtvq" role="jymVt" />
-      <node concept="3clFb_" id="5mr7UHcbuF5" role="jymVt">
-        <property role="1EzhhJ" value="true" />
-        <property role="TrG5h" value="createConfig" />
-        <node concept="3uibUv" id="5mr7UHcbuIP" role="3clF45">
-          <ref role="3uigEE" node="5uFPQ7Bwt8Z" resolve="EvaluationSession.Config" />
-        </node>
-        <node concept="3Tm1VV" id="5mr7UHcbuF8" role="1B3o_S" />
-        <node concept="3clFbS" id="5mr7UHcbuF9" role="3clF47" />
-      </node>
-      <node concept="2tJIrI" id="5mr7UHcbuCs" role="jymVt" />
-      <node concept="3Tmbuc" id="5uFPQ7Bwtsc" role="1B3o_S" />
-    </node>
-    <node concept="2tJIrI" id="5uFPQ7BvQ$M" role="jymVt" />
     <node concept="2YIFZL" id="5uFPQ7Bwt$y" role="jymVt">
       <property role="TrG5h" value="setBackend" />
       <node concept="37vLTG" id="5uFPQ7BwtBf" role="3clF46">
@@ -737,6 +737,33 @@
       <node concept="3Tmbuc" id="5jPBdK_Je4" role="1B3o_S" />
     </node>
     <node concept="2tJIrI" id="5uFPQ7BwtL0" role="jymVt" />
+    <node concept="3HP615" id="5uFPQ7BwtoR" role="jymVt">
+      <property role="2bfB8j" value="true" />
+      <property role="TrG5h" value="Backend" />
+      <node concept="2tJIrI" id="5uFPQ7Bwtqx" role="jymVt" />
+      <node concept="3clFb_" id="5uFPQ7BwtvO" role="jymVt">
+        <property role="1EzhhJ" value="true" />
+        <property role="TrG5h" value="current" />
+        <node concept="3uibUv" id="5uFPQ7BwtwM" role="3clF45">
+          <ref role="3uigEE" node="5uFPQ7BvN_d" resolve="EvaluationSession" />
+        </node>
+        <node concept="3Tm1VV" id="5uFPQ7BwtvR" role="1B3o_S" />
+        <node concept="3clFbS" id="5uFPQ7BwtvS" role="3clF47" />
+      </node>
+      <node concept="2tJIrI" id="5uFPQ7Bwtvq" role="jymVt" />
+      <node concept="3clFb_" id="5mr7UHcbuF5" role="jymVt">
+        <property role="1EzhhJ" value="true" />
+        <property role="TrG5h" value="createConfig" />
+        <node concept="3uibUv" id="5mr7UHcbuIP" role="3clF45">
+          <ref role="3uigEE" node="5uFPQ7Bwt8Z" resolve="EvaluationSession.Config" />
+        </node>
+        <node concept="3Tm1VV" id="5mr7UHcbuF8" role="1B3o_S" />
+        <node concept="3clFbS" id="5mr7UHcbuF9" role="3clF47" />
+      </node>
+      <node concept="2tJIrI" id="5mr7UHcbuCs" role="jymVt" />
+      <node concept="3Tmbuc" id="5uFPQ7Bwtsc" role="1B3o_S" />
+    </node>
+    <node concept="2tJIrI" id="5uFPQ7BvQ$M" role="jymVt" />
     <node concept="Wx3nA" id="5uFPQ7BwtFE" role="jymVt">
       <property role="TrG5h" value="ourBackend" />
       <node concept="3Tm6S6" id="5uFPQ7BwtFG" role="1B3o_S" />
diff --git a/languages/jetbrains.mps.logic/runtime/models/jetbrains/mps/logic/builtin/java.mps b/languages/jetbrains.mps.logic/runtime/models/jetbrains/mps/logic/builtin/java.mps
index fcffd999..1b24397b 100644
--- a/languages/jetbrains.mps.logic/runtime/models/jetbrains/mps/logic/builtin/java.mps
+++ b/languages/jetbrains.mps.logic/runtime/models/jetbrains/mps/logic/builtin/java.mps
@@ -22,12 +22,6 @@
         <child id="1068498886295" name="lValue" index="37vLTJ" />
       </concept>
       <concept id="1465982738277781862" name="jetbrains.mps.baseLanguage.structure.PlaceholderMember" flags="ng" index="2tJIrI" />
-      <concept id="1188207840427" name="jetbrains.mps.baseLanguage.structure.AnnotationInstance" flags="nn" index="2AHcQZ">
-        <reference id="1188208074048" name="annotation" index="2AI5Lk" />
-      </concept>
-      <concept id="1188208481402" name="jetbrains.mps.baseLanguage.structure.HasAnnotation" flags="ng" index="2AJDlI">
-        <child id="1188208488637" name="annotation" index="2AJF6D" />
-      </concept>
       <concept id="1197027756228" name="jetbrains.mps.baseLanguage.structure.DotExpression" flags="nn" index="2OqwBi">
         <child id="1197027771414" name="operand" index="2Oq$k0" />
         <child id="1197027833540" name="operation" index="2OqNvi" />
@@ -40,7 +34,6 @@
       </concept>
       <concept id="1070475354124" name="jetbrains.mps.baseLanguage.structure.ThisExpression" flags="nn" index="Xjq3P" />
       <concept id="1070475587102" name="jetbrains.mps.baseLanguage.structure.SuperConstructorInvocation" flags="nn" index="XkiVB" />
-      <concept id="1070534058343" name="jetbrains.mps.baseLanguage.structure.NullLiteral" flags="nn" index="10Nm6u" />
       <concept id="1068390468200" name="jetbrains.mps.baseLanguage.structure.FieldDeclaration" flags="ig" index="312cEg" />
       <concept id="1068390468198" name="jetbrains.mps.baseLanguage.structure.ClassConcept" flags="ig" index="312cEu">
         <property id="1075300953594" name="abstractClass" index="1sVAO0" />
@@ -79,23 +72,13 @@
       <concept id="1107461130800" name="jetbrains.mps.baseLanguage.structure.Classifier" flags="ng" index="3pOWGL">
         <child id="5375687026011219971" name="member" index="jymVt" unordered="true" />
       </concept>
-      <concept id="1171903916106" name="jetbrains.mps.baseLanguage.structure.UpperBoundType" flags="in" index="3qUE_q">
-        <child id="1171903916107" name="bound" index="3qUE_r" />
-      </concept>
       <concept id="1107535904670" name="jetbrains.mps.baseLanguage.structure.ClassifierType" flags="in" index="3uibUv">
         <reference id="1107535924139" name="classifier" index="3uigEE" />
-        <child id="1109201940907" name="parameter" index="11_B2D" />
       </concept>
       <concept id="1178549954367" name="jetbrains.mps.baseLanguage.structure.IVisible" flags="ng" index="1B3ioH">
         <child id="1178549979242" name="visibility" index="1B3o_S" />
       </concept>
       <concept id="1208890769693" name="jetbrains.mps.baseLanguage.structure.ArrayLengthOperation" flags="nn" index="1Rwk04" />
-      <concept id="6329021646629104957" name="jetbrains.mps.baseLanguage.structure.TextCommentPart" flags="nn" index="3SKdUq">
-        <property id="6329021646629104958" name="text" index="3SKdUp" />
-      </concept>
-      <concept id="6329021646629104954" name="jetbrains.mps.baseLanguage.structure.SingleLineComment" flags="nn" index="3SKdUt">
-        <child id="6329021646629175155" name="commentPart" index="3SKWNk" />
-      </concept>
       <concept id="1146644602865" name="jetbrains.mps.baseLanguage.structure.PublicVisibility" flags="nn" index="3Tm1VV" />
       <concept id="1146644623116" name="jetbrains.mps.baseLanguage.structure.PrivateVisibility" flags="nn" index="3Tm6S6" />
     </language>
@@ -106,7 +89,7 @@
     </language>
   </registry>
   <node concept="312cEu" id="5$WbtTOYoMb">
-    <property role="TrG5h" value="JavaBuiltinConstraint" />
+    <property role="TrG5h" value="JavaPredicate" />
     <property role="1sVAO0" value="false" />
     <node concept="2tJIrI" id="7ISVfSJp0R" role="jymVt" />
     <node concept="312cEg" id="7ISVfSJoWw" role="jymVt">
@@ -166,33 +149,6 @@
       </node>
     </node>
     <node concept="2tJIrI" id="5$WbtTOYoTe" role="jymVt" />
-    <node concept="3clFb_" id="4xBopTzr9Jk" role="jymVt">
-      <property role="1EzhhJ" value="false" />
-      <property role="TrG5h" value="solverClass" />
-      <node concept="3uibUv" id="4xBopTzr9Jl" role="3clF45">
-        <ref role="3uigEE" to="wyt6:~Class" resolve="Class" />
-        <node concept="3qUE_q" id="4xBopTzr9Jm" role="11_B2D">
-          <node concept="3uibUv" id="4xBopTzr9Jn" role="3qUE_r">
-            <ref role="3uigEE" to="qrld:6Kcfpq7AYBh" resolve="Queryable" />
-          </node>
-        </node>
-      </node>
-      <node concept="3Tm1VV" id="4xBopTzr9Jo" role="1B3o_S" />
-      <node concept="3clFbS" id="4xBopTzr9Jr" role="3clF47">
-        <node concept="3SKdUt" id="5uFPQ7CjcNO" role="3cqZAp">
-          <node concept="3SKdUq" id="5uFPQ7CjcNW" role="3SKWNk">
-            <property role="3SKdUp" value="FIXME: implement me" />
-          </node>
-        </node>
-        <node concept="3clFbF" id="5mr7UHclimT" role="3cqZAp">
-          <node concept="10Nm6u" id="5mr7UHclimR" role="3clFbG" />
-        </node>
-      </node>
-      <node concept="2AHcQZ" id="4xBopTzrlec" role="2AJF6D">
-        <ref role="2AI5Lk" to="wyt6:~Override" resolve="Override" />
-      </node>
-    </node>
-    <node concept="2tJIrI" id="5$WbtTOYxH4" role="jymVt" />
     <node concept="3clFb_" id="7ISVfSJoQm" role="jymVt">
       <property role="1EzhhJ" value="false" />
       <property role="TrG5h" value="symbol" />
diff --git a/languages/jetbrains.mps.logic/runtime/models/jetbrains/mps/logic/builtin/unification.mps b/languages/jetbrains.mps.logic/runtime/models/jetbrains/mps/logic/builtin/unification.mps
index a25e4b58..1f652f8b 100644
--- a/languages/jetbrains.mps.logic/runtime/models/jetbrains/mps/logic/builtin/unification.mps
+++ b/languages/jetbrains.mps.logic/runtime/models/jetbrains/mps/logic/builtin/unification.mps
@@ -1091,7 +1091,7 @@
     </node>
   </node>
   <node concept="312cEu" id="2GO7tyJVmP4">
-    <property role="TrG5h" value="UnificationBuiltinConstraint" />
+    <property role="TrG5h" value="UnificationPredicate" />
     <node concept="2tJIrI" id="5uFPQ7C29se" role="jymVt" />
     <node concept="3Tm1VV" id="2GO7tyJVmP5" role="1B3o_S" />
     <node concept="Wx3nA" id="2GO7tyJVob2" role="jymVt">
@@ -1134,21 +1134,6 @@
       </node>
     </node>
     <node concept="2tJIrI" id="2GO7tyJVqjK" role="jymVt" />
-    <node concept="Wx3nA" id="5uFPQ7C5uqZ" role="jymVt">
-      <property role="3TUv4t" value="true" />
-      <property role="TrG5h" value="QUERYABLE" />
-      <node concept="3Tm1VV" id="5uFPQ7C5uqV" role="1B3o_S" />
-      <node concept="3uibUv" id="5uFPQ7C5uqW" role="1tU5fm">
-        <ref role="3uigEE" to="wyt6:~Class" resolve="Class" />
-        <node concept="3uibUv" id="5uFPQ7C5uqX" role="11_B2D">
-          <ref role="3uigEE" to="95zw:6njqcfQVO0n" resolve="UnificationSolver" />
-        </node>
-      </node>
-      <node concept="3VsKOn" id="5uFPQ7C5uqY" role="33vP2m">
-        <ref role="3VsUkX" to="95zw:6njqcfQVO0n" resolve="UnificationSolver" />
-      </node>
-    </node>
-    <node concept="2tJIrI" id="2GO7tyJY8Fs" role="jymVt" />
     <node concept="3clFbW" id="4xBopTzmopz" role="jymVt">
       <node concept="37vLTG" id="5uFPQ7C29xx" role="3clF46">
         <property role="TrG5h" value="left" />
@@ -1177,30 +1162,6 @@
       </node>
     </node>
     <node concept="2tJIrI" id="4xBopTzmo93" role="jymVt" />
-    <node concept="3clFb_" id="4xBopTzmp95" role="jymVt">
-      <property role="1EzhhJ" value="false" />
-      <property role="TrG5h" value="solverClass" />
-      <node concept="3uibUv" id="4xBopTzmp96" role="3clF45">
-        <ref role="3uigEE" to="wyt6:~Class" resolve="Class" />
-        <node concept="3qUE_q" id="4xBopTzmp97" role="11_B2D">
-          <node concept="3uibUv" id="4xBopTzmp98" role="3qUE_r">
-            <ref role="3uigEE" to="qrld:6Kcfpq7AYBh" resolve="Queryable" />
-          </node>
-        </node>
-      </node>
-      <node concept="3Tm1VV" id="4xBopTzmp99" role="1B3o_S" />
-      <node concept="3clFbS" id="4xBopTzmp9c" role="3clF47">
-        <node concept="3clFbF" id="4xBopTztl0s" role="3cqZAp">
-          <node concept="37vLTw" id="5uFPQ7C5ur2" role="3clFbG">
-            <ref role="3cqZAo" node="5uFPQ7C5uqZ" resolve="QUERYABLE" />
-          </node>
-        </node>
-      </node>
-      <node concept="2AHcQZ" id="4xBopTznCo5" role="2AJF6D">
-        <ref role="2AI5Lk" to="wyt6:~Override" resolve="Override" />
-      </node>
-    </node>
-    <node concept="2tJIrI" id="4xBopTzmpnW" role="jymVt" />
     <node concept="3clFb_" id="7ISVfSJpsU" role="jymVt">
       <property role="1EzhhJ" value="false" />
       <property role="TrG5h" value="symbol" />
@@ -1858,7 +1819,7 @@
     </node>
   </node>
   <node concept="312cEu" id="3HJTsBn4kk_">
-    <property role="TrG5h" value="EqualsBuiltinConstraint" />
+    <property role="TrG5h" value="EqualsPredicate" />
     <node concept="2tJIrI" id="7ISVfSJmTL" role="jymVt" />
     <node concept="Wx3nA" id="3HJTsBn4kQi" role="jymVt">
       <property role="TrG5h" value="EQ" />
@@ -1900,21 +1861,6 @@
       </node>
     </node>
     <node concept="2tJIrI" id="3HJTsBn4kJ_" role="jymVt" />
-    <node concept="Wx3nA" id="5uFPQ7C5vo9" role="jymVt">
-      <property role="3TUv4t" value="true" />
-      <property role="TrG5h" value="QUERYABLE" />
-      <node concept="3Tm1VV" id="5uFPQ7C5vo5" role="1B3o_S" />
-      <node concept="3uibUv" id="5uFPQ7C5vo6" role="1tU5fm">
-        <ref role="3uigEE" to="wyt6:~Class" resolve="Class" />
-        <node concept="3uibUv" id="5uFPQ7C5vo7" role="11_B2D">
-          <ref role="3uigEE" to="95zw:3HJTsBn4mEA" resolve="EqualsSolver" />
-        </node>
-      </node>
-      <node concept="3VsKOn" id="5uFPQ7C5vo8" role="33vP2m">
-        <ref role="3VsUkX" to="95zw:3HJTsBn4mEA" resolve="EqualsSolver" />
-      </node>
-    </node>
-    <node concept="2tJIrI" id="3HJTsBn4kQx" role="jymVt" />
     <node concept="3clFbW" id="4xBopTzo_Q1" role="jymVt">
       <node concept="37vLTG" id="5uFPQ7C24iY" role="3clF46">
         <property role="TrG5h" value="left" />
@@ -1943,30 +1889,6 @@
       </node>
     </node>
     <node concept="2tJIrI" id="4xBopTzo_yK" role="jymVt" />
-    <node concept="3clFb_" id="4xBopTzopJj" role="jymVt">
-      <property role="1EzhhJ" value="false" />
-      <property role="TrG5h" value="solverClass" />
-      <node concept="3uibUv" id="4xBopTzopJk" role="3clF45">
-        <ref role="3uigEE" to="wyt6:~Class" resolve="Class" />
-        <node concept="3qUE_q" id="4xBopTzopJl" role="11_B2D">
-          <node concept="3uibUv" id="4xBopTzopJm" role="3qUE_r">
-            <ref role="3uigEE" to="qrld:6Kcfpq7AYBh" resolve="Queryable" />
-          </node>
-        </node>
-      </node>
-      <node concept="3Tm1VV" id="4xBopTzopJn" role="1B3o_S" />
-      <node concept="3clFbS" id="4xBopTzopJp" role="3clF47">
-        <node concept="3clFbF" id="4xBopTzorXt" role="3cqZAp">
-          <node concept="37vLTw" id="5uFPQ7C5voc" role="3clFbG">
-            <ref role="3cqZAo" node="5uFPQ7C5vo9" resolve="QUERYABLE" />
-          </node>
-        </node>
-      </node>
-      <node concept="2AHcQZ" id="4xBopTzorrq" role="2AJF6D">
-        <ref role="2AI5Lk" to="wyt6:~Override" resolve="Override" />
-      </node>
-    </node>
-    <node concept="2tJIrI" id="5uFPQ7ClJr0" role="jymVt" />
     <node concept="3clFb_" id="5uFPQ7BZaxa" role="jymVt">
       <property role="1EzhhJ" value="false" />
       <property role="TrG5h" value="symbol" />
@@ -1989,7 +1911,7 @@
     </node>
   </node>
   <node concept="312cEu" id="6infEALAfer">
-    <property role="TrG5h" value="AssertBuiltinConstraint" />
+    <property role="TrG5h" value="AssertPredicate" />
     <node concept="2tJIrI" id="5uFPQ7BZo0w" role="jymVt" />
     <node concept="Wx3nA" id="6infEALAgS7" role="jymVt">
       <property role="TrG5h" value="ASSERT" />
@@ -2021,21 +1943,6 @@
       </node>
     </node>
     <node concept="2tJIrI" id="6infEALAgQp" role="jymVt" />
-    <node concept="Wx3nA" id="5uFPQ7C5wj5" role="jymVt">
-      <property role="3TUv4t" value="true" />
-      <property role="TrG5h" value="QUERYABLE" />
-      <node concept="3Tm1VV" id="5uFPQ7C5wj1" role="1B3o_S" />
-      <node concept="3uibUv" id="5uFPQ7C5wj2" role="1tU5fm">
-        <ref role="3uigEE" to="wyt6:~Class" resolve="Class" />
-        <node concept="3uibUv" id="5uFPQ7C5wj3" role="11_B2D">
-          <ref role="3uigEE" to="95zw:6infEALA98Q" resolve="AssertSolver" />
-        </node>
-      </node>
-      <node concept="3VsKOn" id="5uFPQ7C5wj4" role="33vP2m">
-        <ref role="3VsUkX" to="95zw:6infEALA98Q" resolve="AssertSolver" />
-      </node>
-    </node>
-    <node concept="2tJIrI" id="4xBopTzrPN8" role="jymVt" />
     <node concept="3clFbW" id="4xBopTzrPWl" role="jymVt">
       <node concept="37vLTG" id="5uFPQ7C251x" role="3clF46">
         <property role="TrG5h" value="expression" />
@@ -2055,30 +1962,6 @@
       </node>
     </node>
     <node concept="2tJIrI" id="4xBopTzrQOJ" role="jymVt" />
-    <node concept="3clFb_" id="4xBopTzs1xV" role="jymVt">
-      <property role="1EzhhJ" value="false" />
-      <property role="TrG5h" value="solverClass" />
-      <node concept="3uibUv" id="4xBopTzs1xW" role="3clF45">
-        <ref role="3uigEE" to="wyt6:~Class" resolve="Class" />
-        <node concept="3qUE_q" id="4xBopTzs1xX" role="11_B2D">
-          <node concept="3uibUv" id="4xBopTzs1xY" role="3qUE_r">
-            <ref role="3uigEE" to="qrld:6Kcfpq7AYBh" resolve="Queryable" />
-          </node>
-        </node>
-      </node>
-      <node concept="3Tm1VV" id="4xBopTzs1xZ" role="1B3o_S" />
-      <node concept="3clFbS" id="4xBopTzs1y2" role="3clF47">
-        <node concept="3clFbF" id="4xBopTzs3gC" role="3cqZAp">
-          <node concept="37vLTw" id="5uFPQ7C5wj8" role="3clFbG">
-            <ref role="3cqZAo" node="5uFPQ7C5wj5" resolve="QUERYABLE" />
-          </node>
-        </node>
-      </node>
-      <node concept="2AHcQZ" id="4xBopTzs4eK" role="2AJF6D">
-        <ref role="2AI5Lk" to="wyt6:~Override" resolve="Override" />
-      </node>
-    </node>
-    <node concept="2tJIrI" id="7ISVfSJpjm" role="jymVt" />
     <node concept="3clFb_" id="7ISVfSJpfI" role="jymVt">
       <property role="1EzhhJ" value="false" />
       <property role="TrG5h" value="symbol" />
diff --git a/languages/jetbrains.mps.logic/runtime/models/jetbrains/mps/logic/builtin/var.mps b/languages/jetbrains.mps.logic/runtime/models/jetbrains/mps/logic/builtin/var.mps
index 0e9ba170..0a38ee9c 100644
--- a/languages/jetbrains.mps.logic/runtime/models/jetbrains/mps/logic/builtin/var.mps
+++ b/languages/jetbrains.mps.logic/runtime/models/jetbrains/mps/logic/builtin/var.mps
@@ -114,13 +114,9 @@
       <concept id="1107461130800" name="jetbrains.mps.baseLanguage.structure.Classifier" flags="ng" index="3pOWGL">
         <child id="5375687026011219971" name="member" index="jymVt" unordered="true" />
       </concept>
-      <concept id="1171903916106" name="jetbrains.mps.baseLanguage.structure.UpperBoundType" flags="in" index="3qUE_q">
-        <child id="1171903916107" name="bound" index="3qUE_r" />
-      </concept>
       <concept id="7812454656619025412" name="jetbrains.mps.baseLanguage.structure.LocalMethodCall" flags="nn" index="1rXfSq" />
       <concept id="1107535904670" name="jetbrains.mps.baseLanguage.structure.ClassifierType" flags="in" index="3uibUv">
         <reference id="1107535924139" name="classifier" index="3uigEE" />
-        <child id="1109201940907" name="parameter" index="11_B2D" />
       </concept>
       <concept id="1081773326031" name="jetbrains.mps.baseLanguage.structure.BinaryOperation" flags="nn" index="3uHJSO">
         <child id="1081773367579" name="rightExpression" index="3uHU7w" />
@@ -131,9 +127,6 @@
       </concept>
       <concept id="1146644602865" name="jetbrains.mps.baseLanguage.structure.PublicVisibility" flags="nn" index="3Tm1VV" />
       <concept id="1146644623116" name="jetbrains.mps.baseLanguage.structure.PrivateVisibility" flags="nn" index="3Tm6S6" />
-      <concept id="1116615150612" name="jetbrains.mps.baseLanguage.structure.ClassifierClassExpression" flags="nn" index="3VsKOn">
-        <reference id="1116615189566" name="classifier" index="3VsUkX" />
-      </concept>
     </language>
     <language id="ceab5195-25ea-4f22-9b92-103b95ca8c0c" name="jetbrains.mps.lang.core">
       <concept id="1169194658468" name="jetbrains.mps.lang.core.structure.INamedConcept" flags="ng" index="TrEIO">
@@ -142,7 +135,7 @@
     </language>
   </registry>
   <node concept="312cEu" id="5$WbtTOYoMb">
-    <property role="TrG5h" value="LogicalBuiltinConstraint" />
+    <property role="TrG5h" value="LogicalPredicate" />
     <property role="1sVAO0" value="false" />
     <node concept="2tJIrI" id="5$WbtTOYpQU" role="jymVt" />
     <node concept="Wx3nA" id="5uFPQ7C26$b" role="jymVt">
@@ -185,21 +178,6 @@
       </node>
     </node>
     <node concept="2tJIrI" id="5uFPQ7C26l9" role="jymVt" />
-    <node concept="Wx3nA" id="5uFPQ7C5xrx" role="jymVt">
-      <property role="3TUv4t" value="true" />
-      <property role="TrG5h" value="QUERYABLE" />
-      <node concept="3Tm1VV" id="5uFPQ7C5xrt" role="1B3o_S" />
-      <node concept="3uibUv" id="5uFPQ7C5xru" role="1tU5fm">
-        <ref role="3uigEE" to="wyt6:~Class" resolve="Class" />
-        <node concept="3uibUv" id="5uFPQ7C5xrv" role="11_B2D">
-          <ref role="3uigEE" to="95zw:60B5zVEZP8W" resolve="LogicalSolver" />
-        </node>
-      </node>
-      <node concept="3VsKOn" id="5uFPQ7C5xrw" role="33vP2m">
-        <ref role="3VsUkX" to="95zw:60B5zVEZP8W" resolve="LogicalSolver" />
-      </node>
-    </node>
-    <node concept="2tJIrI" id="5uFPQ7C5xWt" role="jymVt" />
     <node concept="2YIFZL" id="5uFPQ7CiPYx" role="jymVt">
       <property role="TrG5h" value="BOUND" />
       <node concept="37vLTG" id="5uFPQ7CiQiV" role="3clF46">
@@ -209,14 +187,14 @@
         </node>
       </node>
       <node concept="3uibUv" id="5uFPQ7CiQa_" role="3clF45">
-        <ref role="3uigEE" node="5$WbtTOYoMb" resolve="LogicalBuiltinConstraint" />
+        <ref role="3uigEE" node="5$WbtTOYoMb" resolve="LogicalPredicate" />
       </node>
       <node concept="3Tm1VV" id="5uFPQ7CiPY$" role="1B3o_S" />
       <node concept="3clFbS" id="5uFPQ7CiPY_" role="3clF47">
         <node concept="3clFbF" id="5uFPQ7CiQsb" role="3cqZAp">
           <node concept="2ShNRf" id="5uFPQ7CiQsd" role="3clFbG">
             <node concept="1pGfFk" id="5uFPQ7CiQse" role="2ShVmc">
-              <ref role="37wK5l" node="5$WbtTOYsLU" resolve="LogicalBuiltinConstraint" />
+              <ref role="37wK5l" node="5$WbtTOYsLU" resolve="LogicalPredicate" />
               <node concept="37vLTw" id="5uFPQ7CiQsz" role="37wK5m">
                 <ref role="3cqZAo" node="5uFPQ7C26$b" resolve="BOUND_SYM" />
               </node>
@@ -243,14 +221,14 @@
         </node>
       </node>
       <node concept="3uibUv" id="5uFPQ7CiQEg" role="3clF45">
-        <ref role="3uigEE" node="5$WbtTOYoMb" resolve="LogicalBuiltinConstraint" />
+        <ref role="3uigEE" node="5$WbtTOYoMb" resolve="LogicalPredicate" />
       </node>
       <node concept="3Tm1VV" id="5uFPQ7CiQEh" role="1B3o_S" />
       <node concept="3clFbS" id="5uFPQ7CiQEi" role="3clF47">
         <node concept="3clFbF" id="5uFPQ7CiQEj" role="3cqZAp">
           <node concept="2ShNRf" id="5uFPQ7CiQEk" role="3clFbG">
             <node concept="1pGfFk" id="5uFPQ7CiQEl" role="2ShVmc">
-              <ref role="37wK5l" node="5$WbtTOYsLU" resolve="LogicalBuiltinConstraint" />
+              <ref role="37wK5l" node="5$WbtTOYsLU" resolve="LogicalPredicate" />
               <node concept="37vLTw" id="5uFPQ7CiRlW" role="37wK5m">
                 <ref role="3cqZAo" node="5uFPQ7C279$" resolve="FREE_SYM" />
               </node>
@@ -312,30 +290,6 @@
       </node>
     </node>
     <node concept="2tJIrI" id="5$WbtTOYoTe" role="jymVt" />
-    <node concept="3clFb_" id="4xBopTzr9Jk" role="jymVt">
-      <property role="1EzhhJ" value="false" />
-      <property role="TrG5h" value="solverClass" />
-      <node concept="3uibUv" id="4xBopTzr9Jl" role="3clF45">
-        <ref role="3uigEE" to="wyt6:~Class" resolve="Class" />
-        <node concept="3qUE_q" id="4xBopTzr9Jm" role="11_B2D">
-          <node concept="3uibUv" id="4xBopTzr9Jn" role="3qUE_r">
-            <ref role="3uigEE" to="qrld:6Kcfpq7AYBh" resolve="Queryable" />
-          </node>
-        </node>
-      </node>
-      <node concept="3Tm1VV" id="4xBopTzr9Jo" role="1B3o_S" />
-      <node concept="3clFbS" id="4xBopTzr9Jr" role="3clF47">
-        <node concept="3clFbF" id="4xBopTzrc89" role="3cqZAp">
-          <node concept="37vLTw" id="5uFPQ7C5xr$" role="3clFbG">
-            <ref role="3cqZAo" node="5uFPQ7C5xrx" resolve="QUERYABLE" />
-          </node>
-        </node>
-      </node>
-      <node concept="2AHcQZ" id="4xBopTzrlec" role="2AJF6D">
-        <ref role="2AI5Lk" to="wyt6:~Override" resolve="Override" />
-      </node>
-    </node>
-    <node concept="2tJIrI" id="5$WbtTOYxH4" role="jymVt" />
     <node concept="3clFb_" id="7ISVfSJpIT" role="jymVt">
       <property role="1EzhhJ" value="false" />
       <property role="TrG5h" value="symbol" />
diff --git a/languages/jetbrains.mps.logic/sandbox/runner/models/jetbrains/mps/logic/sandbox/runner.mps b/languages/jetbrains.mps.logic/sandbox/runner/models/jetbrains/mps/logic/sandbox/runner.mps
index 79b183e0..0d2d3cb4 100644
--- a/languages/jetbrains.mps.logic/sandbox/runner/models/jetbrains/mps/logic/sandbox/runner.mps
+++ b/languages/jetbrains.mps.logic/sandbox/runner/models/jetbrains/mps/logic/sandbox/runner.mps
@@ -24,6 +24,9 @@
         <child id="1173175577737" name="index" index="AHEQo" />
         <child id="1173175590490" name="array" index="AHHXb" />
       </concept>
+      <concept id="2820489544401957797" name="jetbrains.mps.baseLanguage.structure.DefaultClassCreator" flags="nn" index="HV5vD">
+        <reference id="2820489544401957798" name="classifier" index="HV5vE" />
+      </concept>
       <concept id="1154032098014" name="jetbrains.mps.baseLanguage.structure.AbstractLoopStatement" flags="nn" index="2LF5Ji">
         <child id="1154032183016" name="body" index="2LFqv$" />
       </concept>
@@ -38,9 +41,6 @@
         <property id="1070475926801" name="value" index="Xl_RC" />
       </concept>
       <concept id="1081236700938" name="jetbrains.mps.baseLanguage.structure.StaticMethodDeclaration" flags="ig" index="2YIFZL" />
-      <concept id="1081236700937" name="jetbrains.mps.baseLanguage.structure.StaticMethodCall" flags="nn" index="2YIFZM">
-        <reference id="1144433194310" name="classConcept" index="1Pybhc" />
-      </concept>
       <concept id="1070533707846" name="jetbrains.mps.baseLanguage.structure.StaticFieldReference" flags="nn" index="10M0yZ">
         <reference id="1144433057691" name="classifier" index="1PxDUh" />
       </concept>
@@ -169,6 +169,37 @@
       <node concept="3cqZAl" id="5lJXKt5l6" role="3clF45" />
       <node concept="3Tm1VV" id="5lJXKt5l7" role="1B3o_S" />
       <node concept="3clFbS" id="5lJXKt5l8" role="3clF47">
+        <node concept="3cpWs8" id="2tcGHBEiwI2" role="3cqZAp">
+          <node concept="3cpWsn" id="2tcGHBEiwI3" role="3cpWs9">
+            <property role="TrG5h" value="symbols" />
+            <node concept="3uibUv" id="2tcGHBEiwHZ" role="1tU5fm">
+              <ref role="3uigEE" to="95zw:7ISVfSIxNO" resolve="Symbols" />
+            </node>
+            <node concept="2ShNRf" id="2tcGHBEiwI4" role="33vP2m">
+              <node concept="HV5vD" id="2tcGHBEiAJP" role="2ShVmc">
+                <ref role="HV5vE" to="95zw:7ISVfSIxNO" resolve="Symbols" />
+              </node>
+            </node>
+          </node>
+        </node>
+        <node concept="3clFbF" id="2tcGHBEiwVK" role="3cqZAp">
+          <node concept="2OqwBi" id="2tcGHBEix1e" role="3clFbG">
+            <node concept="37vLTw" id="2tcGHBEiwVI" role="2Oq$k0">
+              <ref role="3cqZAo" node="2tcGHBEiwI3" resolve="symbols" />
+            </node>
+            <node concept="liA8E" id="2tcGHBEix5E" role="2OqNvi">
+              <ref role="37wK5l" to="qrld:2tcGHBEeol1" resolve="init" />
+              <node concept="10M0yZ" id="qubcdttZN1" role="37wK5m">
+                <ref role="3cqZAo" to="oy3s:5uFPQ7C23RV" resolve="EQ_SYM" />
+                <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
+              </node>
+              <node concept="10M0yZ" id="qubcdttZN4" role="37wK5m">
+                <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
+                <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
+              </node>
+            </node>
+          </node>
+        </node>
         <node concept="3cpWs8" id="5lJXKt5l9" role="3cqZAp">
           <node concept="3cpWsn" id="5lJXKt5la" role="3cpWs9">
             <property role="TrG5h" value="handler" />
@@ -181,22 +212,8 @@
                 <node concept="2ShNRf" id="5lJXKt5le" role="1KkMwq">
                   <node concept="1pGfFk" id="5lJXKt5lf" role="2ShVmc">
                     <ref role="37wK5l" to="95zw:3HJTsBn5KhD" resolve="UnificationSolverImpl" />
-                    <node concept="2OqwBi" id="qubcdtu07G" role="37wK5m">
-                      <node concept="2YIFZM" id="qubcdttZMi" role="2Oq$k0">
-                        <ref role="37wK5l" to="qrld:6Kcfpq7BWKD" resolve="with" />
-                        <ref role="1Pybhc" to="qrld:6Kcfpq7B0b0" resolve="ComputingSession" />
-                        <node concept="10M0yZ" id="qubcdttZN1" role="37wK5m">
-                          <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
-                          <ref role="3cqZAo" to="oy3s:5uFPQ7C23RV" resolve="EQ_SYM" />
-                        </node>
-                        <node concept="10M0yZ" id="qubcdttZN4" role="37wK5m">
-                          <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
-                          <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
-                        </node>
-                      </node>
-                      <node concept="liA8E" id="qubcdtu0th" role="2OqNvi">
-                        <ref role="37wK5l" to="qrld:6Kcfpq7Cgrc" resolve="newSession" />
-                      </node>
+                    <node concept="37vLTw" id="2tcGHBEiwI7" role="37wK5m">
+                      <ref role="3cqZAo" node="2tcGHBEiwI3" resolve="symbols" />
                     </node>
                     <node concept="10Nm6u" id="5uFPQ7CmtB4" role="37wK5m" />
                   </node>
diff --git a/languages/jetbrains.mps.logic/test/jetbrains.mps.logic.test.msd b/languages/jetbrains.mps.logic/test/jetbrains.mps.logic.test.msd
index 207e6cc8..d96a175f 100644
--- a/languages/jetbrains.mps.logic/test/jetbrains.mps.logic.test.msd
+++ b/languages/jetbrains.mps.logic/test/jetbrains.mps.logic.test.msd
@@ -18,7 +18,7 @@
     <dependency reexport="false">a5478664-6b44-4c62-a9f7-434f8aa57eee(jetbrains.mps.logic.runtime)</dependency>
     <dependency reexport="false">b984ee52-f34d-4b6d-8812-866c1d3eae31(jetbrains.mps.jchr.runtime)</dependency>
     <dependency reexport="false">6354ebe7-c22a-4a0f-ac54-50b52ab9b065(JDK)</dependency>
-    <dependency reexport="false">bbf5c548-7111-4a53-a117-cdefc664cf34(jetbrains.mps.logic.reactor)</dependency>
+    <dependency reexport="true">bbf5c548-7111-4a53-a117-cdefc664cf34(jetbrains.mps.logic.reactor)</dependency>
     <dependency reexport="false">760652ad-c01a-495e-9510-ed51532f617b(jetbrains.mps.logic.jchr)</dependency>
     <dependency reexport="false">e4a4c488-aaf8-4c5b-bc98-e65c5dd9acb9(jetbrains.mps.lang.typesystem2.samplechecker.handler.test)</dependency>
   </dependencies>
diff --git a/languages/jetbrains.mps.logic/test/models/jetbrains/mps/logic/test/unification.mps b/languages/jetbrains.mps.logic/test/models/jetbrains/mps/logic/test/unification.mps
index e6da417a..b6ced03e 100644
--- a/languages/jetbrains.mps.logic/test/models/jetbrains/mps/logic/test/unification.mps
+++ b/languages/jetbrains.mps.logic/test/models/jetbrains/mps/logic/test/unification.mps
@@ -1610,27 +1610,49 @@
             </node>
           </node>
         </node>
+        <node concept="3cpWs8" id="2tcGHBEiyPe" role="3cqZAp">
+          <node concept="3cpWsn" id="2tcGHBEiyPf" role="3cpWs9">
+            <property role="TrG5h" value="symbols" />
+            <node concept="3uibUv" id="2tcGHBEiyPc" role="1tU5fm">
+              <ref role="3uigEE" to="95zw:7ISVfSIxNO" resolve="JchrSolver" />
+            </node>
+            <node concept="2ShNRf" id="2tcGHBEiyPg" role="33vP2m">
+              <node concept="HV5vD" id="2tcGHBEiB2V" role="2ShVmc">
+                <ref role="HV5vE" to="95zw:7ISVfSIxNO" resolve="JchrSolver" />
+              </node>
+            </node>
+          </node>
+        </node>
+        <node concept="3SKdUt" id="2tcGHBEi$SM" role="3cqZAp">
+          <node concept="3SKdUq" id="2tcGHBEi$SO" role="3SKWNk">
+            <property role="3SKdUp" value="TODO: why create new solvers?" />
+          </node>
+        </node>
+        <node concept="3clFbF" id="2tcGHBEiyVs" role="3cqZAp">
+          <node concept="2OqwBi" id="2tcGHBEiyYu" role="3clFbG">
+            <node concept="37vLTw" id="2tcGHBEiyVq" role="2Oq$k0">
+              <ref role="3cqZAo" node="2tcGHBEiyPf" resolve="symbols" />
+            </node>
+            <node concept="liA8E" id="2tcGHBEiz1l" role="2OqNvi">
+              <ref role="37wK5l" to="qrld:2tcGHBEeol1" resolve="init" />
+              <node concept="10M0yZ" id="qubcdttZN1" role="37wK5m">
+                <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
+                <ref role="3cqZAo" to="oy3s:5uFPQ7C23RV" resolve="EQ_SYM" />
+              </node>
+              <node concept="10M0yZ" id="qubcdttZN4" role="37wK5m">
+                <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
+                <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
+              </node>
+            </node>
+          </node>
+        </node>
         <node concept="3clFbF" id="fHk0tWuoLS" role="3cqZAp">
           <node concept="37vLTI" id="fHk0tWuoPJ" role="3clFbG">
             <node concept="2ShNRf" id="fHk0tWuoQm" role="37vLTx">
               <node concept="1pGfFk" id="fHk0tWutdI" role="2ShVmc">
                 <ref role="37wK5l" to="95zw:5p8T3QHGKJ7" resolve="UnificationSolverImpl" />
-                <node concept="2OqwBi" id="qubcdtu0uA" role="37wK5m">
-                  <node concept="2YIFZM" id="qubcdtu0uB" role="2Oq$k0">
-                    <ref role="37wK5l" to="qrld:6Kcfpq7BWKD" resolve="with" />
-                    <ref role="1Pybhc" to="qrld:6Kcfpq7B0b0" resolve="ComputingSession" />
-                    <node concept="10M0yZ" id="qubcdtu0uC" role="37wK5m">
-                      <ref role="3cqZAo" to="oy3s:5uFPQ7C23RV" resolve="EQ_SYM" />
-                      <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
-                    </node>
-                    <node concept="10M0yZ" id="qubcdtu0uD" role="37wK5m">
-                      <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
-                      <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
-                    </node>
-                  </node>
-                  <node concept="liA8E" id="qubcdtu0uE" role="2OqNvi">
-                    <ref role="37wK5l" to="qrld:6Kcfpq7Cgrc" resolve="newSession" />
-                  </node>
+                <node concept="37vLTw" id="2tcGHBEiyPi" role="37wK5m">
+                  <ref role="3cqZAo" node="2tcGHBEiyPf" resolve="symbols" />
                 </node>
                 <node concept="37vLTw" id="fHk0tWutiw" role="37wK5m">
                   <ref role="3cqZAo" node="71LvIRuyoUF" resolve="constraintSystem" />
@@ -1651,15 +1673,7 @@
   </node>
   <node concept="3s_ewN" id="1OShD0IfsNp">
     <property role="3s_ewP" value="TellUniSolver" />
-    <node concept="312cEg" id="1OShD0Ift_O" role="jymVt">
-      <property role="TrG5h" value="constraintSystem" />
-      <node concept="3Tm6S6" id="1OShD0Ift_P" role="1B3o_S" />
-      <node concept="3uibUv" id="1OShD0Ift_Q" role="1tU5fm">
-        <ref role="3uigEE" to="eifs:~ConstraintSystem" resolve="ConstraintSystem" />
-      </node>
-    </node>
-    <node concept="2tJIrI" id="5jPBdKMIHL" role="jymVt" />
-    <node concept="2tJIrI" id="1OShD0Ifu78" role="jymVt" />
+    <node concept="2tJIrI" id="2tcGHBEipQe" role="jymVt" />
     <node concept="3clFb_" id="1OShD0Ifu8d" role="jymVt">
       <property role="TrG5h" value="var" />
       <node concept="37vLTG" id="1OShD0Ifu8e" role="3clF46">
@@ -1940,13 +1954,13 @@
                   <ref role="1Pybhc" to="rchb:5uFPQ7BvN_d" resolve="EvaluationSession" />
                 </node>
                 <node concept="liA8E" id="5jPBdK_voQ" role="2OqNvi">
-                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="computingSession" />
+                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="sessionSolver" />
                 </node>
               </node>
               <node concept="liA8E" id="5jPBdK_vsV" role="2OqNvi">
                 <ref role="37wK5l" to="qrld:4xBopTznPKO" resolve="tell" />
                 <node concept="10M0yZ" id="5jPBdK_vv8" role="37wK5m">
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
                 </node>
                 <node concept="37vLTw" id="5jPBdKNF6V" role="37wK5m">
@@ -2077,13 +2091,13 @@
                   <ref role="37wK5l" to="rchb:5uFPQ7Bwt5n" resolve="current" />
                 </node>
                 <node concept="liA8E" id="5jPBdKNFjm" role="2OqNvi">
-                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="computingSession" />
+                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="sessionSolver" />
                 </node>
               </node>
               <node concept="liA8E" id="5jPBdKNFjn" role="2OqNvi">
                 <ref role="37wK5l" to="qrld:4xBopTznPKO" resolve="tell" />
                 <node concept="10M0yZ" id="5jPBdKNFjo" role="37wK5m">
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
                 </node>
                 <node concept="37vLTw" id="5jPBdKNFjp" role="37wK5m">
@@ -2258,13 +2272,13 @@
                   <ref role="1Pybhc" to="rchb:5uFPQ7BvN_d" resolve="EvaluationSession" />
                 </node>
                 <node concept="liA8E" id="5jPBdKNFBa" role="2OqNvi">
-                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="computingSession" />
+                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="sessionSolver" />
                 </node>
               </node>
               <node concept="liA8E" id="5jPBdKNFBb" role="2OqNvi">
                 <ref role="37wK5l" to="qrld:4xBopTznHV5" resolve="ask" />
                 <node concept="10M0yZ" id="5jPBdKNFBc" role="37wK5m">
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
                 </node>
                 <node concept="37vLTw" id="5jPBdKNFBd" role="37wK5m">
@@ -2285,13 +2299,13 @@
                   <ref role="37wK5l" to="rchb:5uFPQ7Bwt5n" resolve="current" />
                 </node>
                 <node concept="liA8E" id="5jPBdKNFL8" role="2OqNvi">
-                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="computingSession" />
+                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="sessionSolver" />
                 </node>
               </node>
               <node concept="liA8E" id="5jPBdKNFL9" role="2OqNvi">
                 <ref role="37wK5l" to="qrld:4xBopTznPKO" resolve="tell" />
                 <node concept="10M0yZ" id="5jPBdKNFLa" role="37wK5m">
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
                 </node>
                 <node concept="37vLTw" id="5jPBdKNFLb" role="37wK5m">
@@ -2338,13 +2352,13 @@
                   <ref role="37wK5l" to="rchb:5uFPQ7Bwt5n" resolve="current" />
                 </node>
                 <node concept="liA8E" id="5jPBdKNG7g" role="2OqNvi">
-                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="computingSession" />
+                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="sessionSolver" />
                 </node>
               </node>
               <node concept="liA8E" id="5jPBdKNG7h" role="2OqNvi">
                 <ref role="37wK5l" to="qrld:4xBopTznHV5" resolve="ask" />
                 <node concept="10M0yZ" id="5jPBdKNG7i" role="37wK5m">
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
                 </node>
                 <node concept="37vLTw" id="5jPBdKNGcw" role="37wK5m">
@@ -2486,14 +2500,14 @@
                   <ref role="37wK5l" to="rchb:5uFPQ7Bwt5n" resolve="current" />
                 </node>
                 <node concept="liA8E" id="5jPBdKNGmi" role="2OqNvi">
-                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="computingSession" />
+                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="sessionSolver" />
                 </node>
               </node>
               <node concept="liA8E" id="5jPBdKNGmj" role="2OqNvi">
                 <ref role="37wK5l" to="qrld:4xBopTznPKO" resolve="tell" />
                 <node concept="10M0yZ" id="5jPBdKNGmk" role="37wK5m">
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                 </node>
                 <node concept="37vLTw" id="5jPBdKNGml" role="37wK5m">
                   <ref role="3cqZAo" node="1OShD0IfNC5" resolve="a" />
@@ -2512,14 +2526,14 @@
                   <ref role="37wK5l" to="rchb:5uFPQ7Bwt5n" resolve="current" />
                 </node>
                 <node concept="liA8E" id="5jPBdKNGuE" role="2OqNvi">
-                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="computingSession" />
+                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="sessionSolver" />
                 </node>
               </node>
               <node concept="liA8E" id="5jPBdKNGuF" role="2OqNvi">
                 <ref role="37wK5l" to="qrld:4xBopTznPKO" resolve="tell" />
                 <node concept="10M0yZ" id="5jPBdKNGuG" role="37wK5m">
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                 </node>
                 <node concept="37vLTw" id="5jPBdKNGCr" role="37wK5m">
                   <ref role="3cqZAo" node="1OShD0IfNCg" resolve="b" />
@@ -2620,14 +2634,14 @@
                   <ref role="1Pybhc" to="rchb:5uFPQ7BvN_d" resolve="EvaluationSession" />
                 </node>
                 <node concept="liA8E" id="5jPBdKNGSC" role="2OqNvi">
-                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="computingSession" />
+                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="sessionSolver" />
                 </node>
               </node>
               <node concept="liA8E" id="5jPBdKNGSD" role="2OqNvi">
                 <ref role="37wK5l" to="qrld:4xBopTznHV5" resolve="ask" />
                 <node concept="10M0yZ" id="5jPBdKNGSE" role="37wK5m">
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                 </node>
                 <node concept="37vLTw" id="5jPBdKNGZw" role="37wK5m">
                   <ref role="3cqZAo" node="1OShD0IfO_f" resolve="s" />
@@ -2769,13 +2783,13 @@
                   <ref role="37wK5l" to="rchb:5uFPQ7Bwt5n" resolve="current" />
                 </node>
                 <node concept="liA8E" id="5jPBdKNHhX" role="2OqNvi">
-                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="computingSession" />
+                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="sessionSolver" />
                 </node>
               </node>
               <node concept="liA8E" id="5jPBdKNHhY" role="2OqNvi">
                 <ref role="37wK5l" to="qrld:4xBopTznPKO" resolve="tell" />
                 <node concept="10M0yZ" id="5jPBdKNHhZ" role="37wK5m">
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
                 </node>
                 <node concept="37vLTw" id="5jPBdKNHH2" role="37wK5m">
@@ -2795,14 +2809,14 @@
                   <ref role="37wK5l" to="rchb:5uFPQ7Bwt5n" resolve="current" />
                 </node>
                 <node concept="liA8E" id="5jPBdKNH9v" role="2OqNvi">
-                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="computingSession" />
+                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="sessionSolver" />
                 </node>
               </node>
               <node concept="liA8E" id="5jPBdKNH9w" role="2OqNvi">
                 <ref role="37wK5l" to="qrld:4xBopTznPKO" resolve="tell" />
                 <node concept="10M0yZ" id="5jPBdKNH9x" role="37wK5m">
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                 </node>
                 <node concept="37vLTw" id="5jPBdKNH9y" role="37wK5m">
                   <ref role="3cqZAo" node="4XqG8ivylRf" resolve="b" />
@@ -2903,14 +2917,14 @@
                   <ref role="1Pybhc" to="rchb:5uFPQ7BvN_d" resolve="EvaluationSession" />
                 </node>
                 <node concept="liA8E" id="5jPBdKNHSE" role="2OqNvi">
-                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="computingSession" />
+                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="sessionSolver" />
                 </node>
               </node>
               <node concept="liA8E" id="5jPBdKNHSF" role="2OqNvi">
                 <ref role="37wK5l" to="qrld:4xBopTznHV5" resolve="ask" />
                 <node concept="10M0yZ" id="5jPBdKNHSG" role="37wK5m">
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                 </node>
                 <node concept="37vLTw" id="5jPBdKNHSH" role="37wK5m">
                   <ref role="3cqZAo" node="4XqG8ivylS2" resolve="s" />
@@ -3029,13 +3043,13 @@
                   <ref role="1Pybhc" to="rchb:5uFPQ7BvN_d" resolve="EvaluationSession" />
                 </node>
                 <node concept="liA8E" id="5jPBdKNHZC" role="2OqNvi">
-                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="computingSession" />
+                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="sessionSolver" />
                 </node>
               </node>
               <node concept="liA8E" id="5jPBdKNHZD" role="2OqNvi">
                 <ref role="37wK5l" to="qrld:4xBopTznPKO" resolve="tell" />
                 <node concept="10M0yZ" id="5jPBdKNHZE" role="37wK5m">
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
                 </node>
                 <node concept="37vLTw" id="5jPBdKNHZF" role="37wK5m">
@@ -3097,13 +3111,13 @@
                   <ref role="1Pybhc" to="rchb:5uFPQ7BvN_d" resolve="EvaluationSession" />
                 </node>
                 <node concept="liA8E" id="5jPBdKNI3L" role="2OqNvi">
-                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="computingSession" />
+                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="sessionSolver" />
                 </node>
               </node>
               <node concept="liA8E" id="5jPBdKNI3M" role="2OqNvi">
                 <ref role="37wK5l" to="qrld:4xBopTznHV5" resolve="ask" />
                 <node concept="10M0yZ" id="5jPBdKNI3N" role="37wK5m">
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
                 </node>
                 <node concept="37vLTw" id="5jPBdKNI3O" role="37wK5m">
@@ -3252,14 +3266,14 @@
                   <ref role="37wK5l" to="rchb:5uFPQ7Bwt5n" resolve="current" />
                 </node>
                 <node concept="liA8E" id="5jPBdKNI6S" role="2OqNvi">
-                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="computingSession" />
+                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="sessionSolver" />
                 </node>
               </node>
               <node concept="liA8E" id="5jPBdKNI6T" role="2OqNvi">
                 <ref role="37wK5l" to="qrld:4xBopTznPKO" resolve="tell" />
                 <node concept="10M0yZ" id="5jPBdKNI6U" role="37wK5m">
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                 </node>
                 <node concept="37vLTw" id="5jPBdKNI6V" role="37wK5m">
                   <ref role="3cqZAo" node="1OShD0IgkRu" resolve="a" />
@@ -3284,14 +3298,14 @@
                   <ref role="37wK5l" to="rchb:5uFPQ7Bwt5n" resolve="current" />
                 </node>
                 <node concept="liA8E" id="5jPBdKNIc1" role="2OqNvi">
-                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="computingSession" />
+                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="sessionSolver" />
                 </node>
               </node>
               <node concept="liA8E" id="5jPBdKNIc2" role="2OqNvi">
                 <ref role="37wK5l" to="qrld:4xBopTznHV5" resolve="ask" />
                 <node concept="10M0yZ" id="5jPBdKNIc3" role="37wK5m">
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                 </node>
                 <node concept="1oi1Uc" id="5jPBdKNIh_" role="37wK5m">
                   <node concept="1oi5UN" id="5jPBdKNIhA" role="1oi0x0">
@@ -3324,14 +3338,14 @@
                   <ref role="37wK5l" to="rchb:5uFPQ7Bwt5n" resolve="current" />
                 </node>
                 <node concept="liA8E" id="5jPBdKNInq" role="2OqNvi">
-                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="computingSession" />
+                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="sessionSolver" />
                 </node>
               </node>
               <node concept="liA8E" id="5jPBdKNInr" role="2OqNvi">
                 <ref role="37wK5l" to="qrld:4xBopTznHV5" resolve="ask" />
                 <node concept="10M0yZ" id="5jPBdKNIns" role="37wK5m">
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                 </node>
                 <node concept="1oi1Uc" id="5jPBdKNIv1" role="37wK5m">
                   <node concept="1oi5UN" id="5jPBdKNIv2" role="1oi0x0">
@@ -3487,14 +3501,14 @@
                   <ref role="37wK5l" to="rchb:5uFPQ7Bwt5n" resolve="current" />
                 </node>
                 <node concept="liA8E" id="5jPBdKNIGb" role="2OqNvi">
-                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="computingSession" />
+                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="sessionSolver" />
                 </node>
               </node>
               <node concept="liA8E" id="5jPBdKNIGc" role="2OqNvi">
                 <ref role="37wK5l" to="qrld:4xBopTznPKO" resolve="tell" />
                 <node concept="10M0yZ" id="5jPBdKNIGd" role="37wK5m">
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                 </node>
                 <node concept="37vLTw" id="5jPBdKNIGe" role="37wK5m">
                   <ref role="3cqZAo" node="1OShD0Ig2i$" resolve="a" />
@@ -3519,14 +3533,14 @@
                   <ref role="37wK5l" to="rchb:5uFPQ7Bwt5n" resolve="current" />
                 </node>
                 <node concept="liA8E" id="5jPBdKNIJO" role="2OqNvi">
-                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="computingSession" />
+                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="sessionSolver" />
                 </node>
               </node>
               <node concept="liA8E" id="5jPBdKNIJP" role="2OqNvi">
                 <ref role="37wK5l" to="qrld:4xBopTznHV5" resolve="ask" />
                 <node concept="10M0yZ" id="5jPBdKNIJQ" role="37wK5m">
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                 </node>
                 <node concept="1oi1Uc" id="5jPBdKNIPU" role="37wK5m">
                   <node concept="KCUsM" id="5jPBdKNIPV" role="1oi0x0">
@@ -3673,13 +3687,13 @@
                   <ref role="1Pybhc" to="rchb:5uFPQ7BvN_d" resolve="EvaluationSession" />
                 </node>
                 <node concept="liA8E" id="5jPBdKNJ04" role="2OqNvi">
-                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="computingSession" />
+                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="sessionSolver" />
                 </node>
               </node>
               <node concept="liA8E" id="5jPBdKNJ05" role="2OqNvi">
                 <ref role="37wK5l" to="qrld:4xBopTznPKO" resolve="tell" />
                 <node concept="10M0yZ" id="5jPBdKNJ06" role="37wK5m">
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
                 </node>
                 <node concept="37vLTw" id="5jPBdKNJ07" role="37wK5m">
@@ -3705,13 +3719,13 @@
                   <ref role="1Pybhc" to="rchb:5uFPQ7BvN_d" resolve="EvaluationSession" />
                 </node>
                 <node concept="liA8E" id="5jPBdKNJ3p" role="2OqNvi">
-                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="computingSession" />
+                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="sessionSolver" />
                 </node>
               </node>
               <node concept="liA8E" id="5jPBdKNJ3q" role="2OqNvi">
                 <ref role="37wK5l" to="qrld:4xBopTznHV5" resolve="ask" />
                 <node concept="10M0yZ" id="5jPBdKNJ3r" role="37wK5m">
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
                 </node>
                 <node concept="1oi1Uc" id="5jPBdKNJ96" role="37wK5m">
@@ -3809,14 +3823,14 @@
                   <ref role="37wK5l" to="rchb:5uFPQ7Bwt5n" resolve="current" />
                 </node>
                 <node concept="liA8E" id="5jPBdKNJfv" role="2OqNvi">
-                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="computingSession" />
+                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="sessionSolver" />
                 </node>
               </node>
               <node concept="liA8E" id="5jPBdKNJfw" role="2OqNvi">
                 <ref role="37wK5l" to="qrld:4xBopTznPKO" resolve="tell" />
                 <node concept="10M0yZ" id="5jPBdKNJfx" role="37wK5m">
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                 </node>
                 <node concept="37vLTw" id="5jPBdKNJfy" role="37wK5m">
                   <ref role="3cqZAo" node="1OShD0Igi9l" resolve="a" />
@@ -3841,13 +3855,13 @@
                   <ref role="1Pybhc" to="rchb:5uFPQ7BvN_d" resolve="EvaluationSession" />
                 </node>
                 <node concept="liA8E" id="5jPBdKNJiC" role="2OqNvi">
-                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="computingSession" />
+                  <ref role="37wK5l" to="rchb:5uFPQ7ClOzA" resolve="sessionSolver" />
                 </node>
               </node>
               <node concept="liA8E" id="5jPBdKNJiD" role="2OqNvi">
                 <ref role="37wK5l" to="qrld:4xBopTznHV5" resolve="ask" />
                 <node concept="10M0yZ" id="5jPBdKNJiE" role="37wK5m">
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
                 </node>
                 <node concept="1oi1Uc" id="5jPBdKNJnX" role="37wK5m">
@@ -3888,10 +3902,10 @@
                 <ref role="37wK5l" to="rchb:5uFPQ7Bwu9Q" resolve="withPredicates" />
                 <node concept="10M0yZ" id="5jPBdK_uXa" role="37wK5m">
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C23RV" resolve="EQ_SYM" />
-                  <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
                 </node>
                 <node concept="10M0yZ" id="5jPBdK_uXd" role="37wK5m">
-                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
+                  <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
                   <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
                 </node>
               </node>
@@ -4697,27 +4711,49 @@
             </node>
           </node>
         </node>
+        <node concept="3cpWs8" id="2tcGHBEi$8m" role="3cqZAp">
+          <node concept="3cpWsn" id="2tcGHBEi$8n" role="3cpWs9">
+            <property role="TrG5h" value="symbols" />
+            <node concept="3uibUv" id="2tcGHBEi$8k" role="1tU5fm">
+              <ref role="3uigEE" to="95zw:7ISVfSIxNO" resolve="JchrSolver" />
+            </node>
+            <node concept="2ShNRf" id="2tcGHBEi$8o" role="33vP2m">
+              <node concept="HV5vD" id="2tcGHBEiBt8" role="2ShVmc">
+                <ref role="HV5vE" to="95zw:7ISVfSIxNO" resolve="JchrSolver" />
+              </node>
+            </node>
+          </node>
+        </node>
+        <node concept="3clFbF" id="2tcGHBEi$gx" role="3cqZAp">
+          <node concept="2OqwBi" id="2tcGHBEi$kw" role="3clFbG">
+            <node concept="37vLTw" id="2tcGHBEi$gv" role="2Oq$k0">
+              <ref role="3cqZAo" node="2tcGHBEi$8n" resolve="symbols" />
+            </node>
+            <node concept="liA8E" id="2tcGHBEi$nn" role="2OqNvi">
+              <ref role="37wK5l" to="qrld:2tcGHBEeol1" resolve="init" />
+              <node concept="10M0yZ" id="2tcGHBEe$iM" role="37wK5m">
+                <ref role="3cqZAo" to="oy3s:5uFPQ7C23RV" resolve="EQ_SYM" />
+                <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsPredicate" />
+              </node>
+              <node concept="10M0yZ" id="2tcGHBEe$iN" role="37wK5m">
+                <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationPredicate" />
+                <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
+              </node>
+            </node>
+          </node>
+        </node>
+        <node concept="3SKdUt" id="2tcGHBEi$_e" role="3cqZAp">
+          <node concept="3SKdUq" id="2tcGHBEi$_g" role="3SKWNk">
+            <property role="3SKdUp" value="TODO: why create new solvers?" />
+          </node>
+        </node>
         <node concept="3clFbF" id="3K_0akS$LUA" role="3cqZAp">
           <node concept="37vLTI" id="3K_0akS$LUB" role="3clFbG">
             <node concept="2ShNRf" id="3K_0akS$LUC" role="37vLTx">
               <node concept="1pGfFk" id="3K_0akS$LUD" role="2ShVmc">
                 <ref role="37wK5l" to="95zw:5p8T3QHGKJ7" resolve="UnificationSolverImpl" />
-                <node concept="2OqwBi" id="5uFPQ7CmmzI" role="37wK5m">
-                  <node concept="2YIFZM" id="5uFPQ7CmmzJ" role="2Oq$k0">
-                    <ref role="1Pybhc" to="qrld:6Kcfpq7B0b0" resolve="ComputingSession" />
-                    <ref role="37wK5l" to="qrld:6Kcfpq7BWKD" resolve="with" />
-                    <node concept="10M0yZ" id="5uFPQ7CmmzK" role="37wK5m">
-                      <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
-                      <ref role="3cqZAo" to="oy3s:5uFPQ7C23RV" resolve="EQ_SYM" />
-                    </node>
-                    <node concept="10M0yZ" id="5uFPQ7CmmzL" role="37wK5m">
-                      <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
-                      <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
-                    </node>
-                  </node>
-                  <node concept="liA8E" id="5uFPQ7CmmzM" role="2OqNvi">
-                    <ref role="37wK5l" to="qrld:6Kcfpq7Cgrc" resolve="newSession" />
-                  </node>
+                <node concept="37vLTw" id="2tcGHBEi$vU" role="37wK5m">
+                  <ref role="3cqZAo" node="2tcGHBEi$8n" resolve="symbols" />
                 </node>
                 <node concept="37vLTw" id="3K_0akS$LUE" role="37wK5m">
                   <ref role="3cqZAo" node="3K_0akS$LOh" resolve="constraintSystem" />
@@ -4735,22 +4771,8 @@
             <node concept="2ShNRf" id="3K_0akS$Mxm" role="37vLTx">
               <node concept="1pGfFk" id="3K_0akS$Mxn" role="2ShVmc">
                 <ref role="37wK5l" to="95zw:5p8T3QHE69j" resolve="EqualsSolverImpl" />
-                <node concept="2OqwBi" id="qubcdttUBY" role="37wK5m">
-                  <node concept="2YIFZM" id="qubcdttUlY" role="2Oq$k0">
-                    <ref role="1Pybhc" to="qrld:6Kcfpq7B0b0" resolve="ComputingSession" />
-                    <ref role="37wK5l" to="qrld:6Kcfpq7BWKD" resolve="with" />
-                    <node concept="10M0yZ" id="4xBopTzqK2f" role="37wK5m">
-                      <ref role="1PxDUh" to="oy3s:3HJTsBn4kk_" resolve="EqualsBuiltinConstraint" />
-                      <ref role="3cqZAo" to="oy3s:5uFPQ7C23RV" resolve="EQ_SYM" />
-                    </node>
-                    <node concept="10M0yZ" id="4xBopTzqK8e" role="37wK5m">
-                      <ref role="3cqZAo" to="oy3s:5uFPQ7C29mw" resolve="UNI_SYM" />
-                      <ref role="1PxDUh" to="oy3s:2GO7tyJVmP4" resolve="UnificationBuiltinConstraint" />
-                    </node>
-                  </node>
-                  <node concept="liA8E" id="qubcdttUF$" role="2OqNvi">
-                    <ref role="37wK5l" to="qrld:6Kcfpq7Cgrc" resolve="newSession" />
-                  </node>
+                <node concept="37vLTw" id="2tcGHBEi$8q" role="37wK5m">
+                  <ref role="3cqZAo" node="2tcGHBEi$8n" resolve="symbols" />
                 </node>
                 <node concept="37vLTw" id="3K_0akS$Mxo" role="37wK5m">
                   <ref role="3cqZAo" node="3K_0akS$LOh" resolve="constraintSystem" />
@@ -4841,51 +4863,39 @@
             <node concept="2OqwBi" id="5jPBdK_qYN" role="37vLTJ">
               <node concept="Xjq3P" id="5jPBdK_qYQ" role="2Oq$k0" />
               <node concept="2OwXpG" id="5jPBdK_qYM" role="2OqNvi">
-                <ref role="2Oxat5" node="5jPBdK_qYD" resolve="computingSession" />
+                <ref role="2Oxat5" node="5jPBdK_qYD" resolve="sessionSolver" />
               </node>
             </node>
             <node concept="37vLTw" id="5jPBdK_qYR" role="37vLTx">
-              <ref role="3cqZAo" node="5jPBdK_qV5" resolve="computingSession" />
+              <ref role="3cqZAo" node="5jPBdK_qV5" resolve="sessionSolver" />
             </node>
           </node>
         </node>
       </node>
       <node concept="37vLTG" id="5jPBdK_qV5" role="3clF46">
-        <property role="TrG5h" value="computingSession" />
+        <property role="TrG5h" value="sessionSolver" />
         <node concept="3uibUv" id="5jPBdK_qV4" role="1tU5fm">
-          <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="ComputingSession" />
+          <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="SessionSolver" />
         </node>
       </node>
     </node>
     <node concept="2tJIrI" id="5jPBdK_qFR" role="jymVt" />
-    <node concept="3clFb_" id="5jPBdK_dWv" role="jymVt">
-      <property role="TrG5h" value="computingTracer" />
-      <property role="1EzhhJ" value="false" />
-      <node concept="3uibUv" id="5jPBdK_dWw" role="3clF45">
-        <ref role="3uigEE" to="qrld:24Vro6cQnrj" resolve="ComputingTracer" />
-      </node>
-      <node concept="3Tm1VV" id="5jPBdK_dWx" role="1B3o_S" />
-      <node concept="3clFbS" id="5jPBdK_dWz" role="3clF47">
-        <node concept="3clFbF" id="5jPBdK_dW_" role="3cqZAp">
-          <node concept="10Nm6u" id="5jPBdK_dW$" role="3clFbG" />
-        </node>
-      </node>
-    </node>
     <node concept="3clFb_" id="5jPBdK_dWA" role="jymVt">
-      <property role="TrG5h" value="computingSession" />
+      <property role="TrG5h" value="sessionSolver" />
       <property role="1EzhhJ" value="false" />
       <node concept="3uibUv" id="5jPBdK_dWB" role="3clF45">
-        <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="ComputingSession" />
+        <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="SessionSolver" />
       </node>
       <node concept="3Tm1VV" id="5jPBdK_dWC" role="1B3o_S" />
       <node concept="3clFbS" id="5jPBdK_dWE" role="3clF47">
         <node concept="3clFbF" id="5jPBdK_r6i" role="3cqZAp">
           <node concept="37vLTw" id="5jPBdK_r6h" role="3clFbG">
-            <ref role="3cqZAo" node="5jPBdK_qYD" resolve="computingSession" />
+            <ref role="3cqZAo" node="5jPBdK_qYD" resolve="sessionSolver" />
           </node>
         </node>
       </node>
     </node>
+    <node concept="2tJIrI" id="2tcGHBEzo4L" role="jymVt" />
     <node concept="3clFb_" id="5jPBdK_dX1" role="jymVt">
       <property role="TrG5h" value="constraintSymbols" />
       <property role="1EzhhJ" value="false" />
@@ -5032,42 +5042,29 @@
         </node>
         <node concept="3Tm1VV" id="5jPBdK_npM" role="1B3o_S" />
         <node concept="3clFbS" id="5jPBdK_npO" role="3clF47">
-          <node concept="3cpWs8" id="5jPBdK_DfG" role="3cqZAp">
-            <node concept="3cpWsn" id="5jPBdK_DfH" role="3cpWs9">
+          <node concept="3cpWs8" id="2tcGHBEewJ$" role="3cqZAp">
+            <node concept="3cpWsn" id="2tcGHBEewJ_" role="3cpWs9">
               <property role="TrG5h" value="csession" />
-              <node concept="3uibUv" id="5jPBdK_DfB" role="1tU5fm">
-                <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="ComputingSession" />
+              <node concept="3uibUv" id="2tcGHBEewJt" role="1tU5fm">
+                <ref role="3uigEE" to="95zw:7ISVfSIxNO" resolve="JchrSolver" />
               </node>
-              <node concept="2OqwBi" id="5jPBdK_DfI" role="33vP2m">
-                <node concept="2YIFZM" id="5jPBdK_DfJ" role="2Oq$k0">
-                  <ref role="37wK5l" to="qrld:6Kcfpq7BWKD" resolve="with" />
-                  <ref role="1Pybhc" to="qrld:6Kcfpq7B0b0" resolve="ComputingSession" />
-                  <node concept="37vLTw" id="5jPBdK_DfK" role="37wK5m">
-                    <ref role="3cqZAo" node="5jPBdK_qdB" resolve="predicateSymbols" />
-                  </node>
-                </node>
-                <node concept="liA8E" id="5jPBdK_DfL" role="2OqNvi">
-                  <ref role="37wK5l" to="qrld:6Kcfpq7Cgrc" resolve="newSession" />
+              <node concept="2ShNRf" id="2tcGHBEewJA" role="33vP2m">
+                <node concept="HV5vD" id="2tcGHBEiBda" role="2ShVmc">
+                  <ref role="HV5vE" to="95zw:7ISVfSIxNO" resolve="JchrSolver" />
                 </node>
               </node>
             </node>
           </node>
           <node concept="3clFbF" id="5jPBdK_B63" role="3cqZAp">
             <node concept="2OqwBi" id="5jPBdK_Bcd" role="3clFbG">
-              <node concept="2ShNRf" id="5jPBdK_BqZ" role="2Oq$k0">
-                <node concept="1pGfFk" id="5jPBdK_Br0" role="2ShVmc">
-                  <ref role="37wK5l" to="95zw:5mr7UHch7og" resolve="Symbols" />
-                  <node concept="37vLTw" id="5jPBdK_DCR" role="37wK5m">
-                    <ref role="3cqZAo" node="5jPBdK_DfH" resolve="csession" />
-                  </node>
-                  <node concept="10Nm6u" id="5jPBdK_DIc" role="37wK5m" />
-                </node>
+              <node concept="37vLTw" id="2tcGHBEewJE" role="2Oq$k0">
+                <ref role="3cqZAo" node="2tcGHBEewJ_" resolve="csession" />
               </node>
               <node concept="liA8E" id="5jPBdK_Bhd" role="2OqNvi">
-                <ref role="37wK5l" to="95zw:5jPBdK__lx" resolve="registerSymbols" />
-                <node concept="2OqwBi" id="5jPBdK_Bie" role="37wK5m">
-                  <node concept="Xjq3P" id="5jPBdK_DL6" role="2Oq$k0" />
-                  <node concept="2OwXpG" id="5jPBdK_Ep_" role="2OqNvi">
+                <ref role="37wK5l" to="qrld:2tcGHBEeol1" resolve="init" />
+                <node concept="2OqwBi" id="2tcGHBEex4W" role="37wK5m">
+                  <node concept="Xjq3P" id="2tcGHBEex4X" role="2Oq$k0" />
+                  <node concept="2OwXpG" id="2tcGHBEex4Y" role="2OqNvi">
                     <ref role="2Oxat5" node="5jPBdK_qdB" resolve="predicateSymbols" />
                   </node>
                 </node>
@@ -5083,7 +5080,7 @@
                 <node concept="1pGfFk" id="5jPBdK_qS9" role="2ShVmc">
                   <ref role="37wK5l" node="5jPBdK_qM0" resolve="TestingEvaluationSession" />
                   <node concept="37vLTw" id="5jPBdK_DfM" role="37wK5m">
-                    <ref role="3cqZAo" node="5jPBdK_DfH" resolve="csession" />
+                    <ref role="3cqZAo" node="2tcGHBEewJ_" resolve="csession" />
                   </node>
                 </node>
               </node>
@@ -5149,10 +5146,10 @@
       <ref role="3uigEE" to="rchb:5uFPQ7BvN_d" resolve="EvaluationSession" />
     </node>
     <node concept="312cEg" id="5jPBdK_qYD" role="jymVt">
-      <property role="TrG5h" value="computingSession" />
+      <property role="TrG5h" value="sessionSolver" />
       <node concept="3Tm6S6" id="5jPBdK_qYE" role="1B3o_S" />
       <node concept="3uibUv" id="5jPBdK_qYG" role="1tU5fm">
-        <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="ComputingSession" />
+        <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="SessionSolver" />
       </node>
     </node>
   </node>
diff --git a/solutions/jetbrains.mps.typechecking.handling/models/jetbrains/mps/typechecking/handler/producer.mps b/solutions/jetbrains.mps.typechecking.handling/models/jetbrains/mps/typechecking/handler/producer.mps
index 774c02cb..79ceebe5 100644
--- a/solutions/jetbrains.mps.typechecking.handling/models/jetbrains/mps/typechecking/handler/producer.mps
+++ b/solutions/jetbrains.mps.typechecking.handling/models/jetbrains/mps/typechecking/handler/producer.mps
@@ -3055,7 +3055,7 @@
           <node concept="22lmx$" id="5uFPQ7BM$Om" role="3clFbw">
             <node concept="3clFbC" id="5uFPQ7BM_cv" role="3uHU7w">
               <node concept="10M0yZ" id="5uFPQ7BM_iX" role="3uHU7w">
-                <ref role="1PxDUh" to="xq5w:5$WbtTOYoMb" resolve="LogicalBuiltinConstraint" />
+                <ref role="1PxDUh" to="xq5w:5$WbtTOYoMb" resolve="LogicalPredicate" />
                 <ref role="3cqZAo" to="xq5w:5uFPQ7C26$b" resolve="BOUND_SYM" />
               </node>
               <node concept="2OqwBi" id="5uFPQ7BM$WD" role="3uHU7B">
@@ -3077,7 +3077,7 @@
                 </node>
               </node>
               <node concept="10M0yZ" id="5uFPQ7BM$Lq" role="3uHU7w">
-                <ref role="1PxDUh" to="xq5w:5$WbtTOYoMb" resolve="LogicalBuiltinConstraint" />
+                <ref role="1PxDUh" to="xq5w:5$WbtTOYoMb" resolve="LogicalPredicate" />
                 <ref role="3cqZAo" to="xq5w:5uFPQ7C279$" resolve="FREE_SYM" />
               </node>
             </node>
@@ -3205,11 +3205,19 @@
                   <node concept="2oxUTD" id="5uFPQ7BMEHf" role="2OqNvi">
                     <node concept="3EllGN" id="5uFPQ7BMEHg" role="2oxUTC">
                       <node concept="2OqwBi" id="7ISVfSJHZy" role="3ElVtu">
-                        <node concept="37vLTw" id="5uFPQ7BRDpm" role="2Oq$k0">
-                          <ref role="3cqZAo" node="5uFPQ7BMz7a" resolve="pred" />
+                        <node concept="37vLTw" id="2tcGHBEqW67" role="2Oq$k0">
+                          <ref role="3cqZAo" node="78CwJJcTKM2" resolve="planningSession" />
                         </node>
                         <node concept="liA8E" id="7ISVfSJI4X" role="2OqNvi">
-                          <ref role="37wK5l" to="qrld:4xBopTzlOsG" resolve="solverClass" />
+                          <ref role="37wK5l" to="rchb:78CwJJcXtfq" resolve="solverClass" />
+                          <node concept="2OqwBi" id="2tcGHBEqWsP" role="37wK5m">
+                            <node concept="37vLTw" id="2tcGHBEqWlH" role="2Oq$k0">
+                              <ref role="3cqZAo" node="5uFPQ7BMz7a" resolve="pred" />
+                            </node>
+                            <node concept="liA8E" id="2tcGHBEqW_3" role="2OqNvi">
+                              <ref role="37wK5l" to="qrld:6Kcfpq7Bjgi" resolve="symbol" />
+                            </node>
+                          </node>
                         </node>
                       </node>
                       <node concept="37vLTw" id="5uFPQ7BMEHn" role="3ElQJh">
@@ -3219,6 +3227,7 @@
                   </node>
                 </node>
               </node>
+              <node concept="3clFbH" id="2tcGHBEqVdZ" role="3cqZAp" />
             </node>
           </node>
         </node>
@@ -6353,6 +6362,9 @@
                       <node concept="37vLTw" id="78CwJJd24mb" role="37wK5m">
                         <ref role="3cqZAo" node="78CwJJd24cM" resolve="name" />
                       </node>
+                      <node concept="37vLTw" id="2tcGHBEqG5y" role="37wK5m">
+                        <ref role="3cqZAo" node="2tcGHBEqFIu" resolve="sessionSolver" />
+                      </node>
                     </node>
                   </node>
                 </node>
@@ -6361,6 +6373,15 @@
                 <property role="TrG5h" value="name" />
                 <node concept="17QB3L" id="78CwJJd24cL" role="1tU5fm" />
               </node>
+              <node concept="37vLTG" id="2tcGHBEqFIu" role="3clF46">
+                <property role="TrG5h" value="sessionSolver" />
+                <node concept="3uibUv" id="2tcGHBEqFRI" role="1tU5fm">
+                  <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="SessionSolver" />
+                </node>
+              </node>
+              <node concept="2AHcQZ" id="2tcGHBEqFVv" role="2AJF6D">
+                <ref role="2AI5Lk" to="wyt6:~Override" resolve="Override" />
+              </node>
             </node>
           </node>
         </node>
@@ -6406,6 +6427,12 @@
         <property role="TrG5h" value="name" />
         <node concept="17QB3L" id="7Oc59RSE6Qh" role="1tU5fm" />
       </node>
+      <node concept="37vLTG" id="2tcGHBEqG6O" role="3clF46">
+        <property role="TrG5h" value="sessionSolver" />
+        <node concept="3uibUv" id="2tcGHBEqGdJ" role="1tU5fm">
+          <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="SessionSolver" />
+        </node>
+      </node>
       <node concept="3cqZAl" id="7eGEHDlcF6b" role="3clF45" />
       <node concept="3Tm6S6" id="78CwJJcTGoj" role="1B3o_S" />
       <node concept="3clFbS" id="7eGEHDlcF6d" role="3clF47">
@@ -6437,6 +6464,19 @@
             </node>
           </node>
         </node>
+        <node concept="3clFbF" id="2tcGHBEqGgQ" role="3cqZAp">
+          <node concept="37vLTI" id="2tcGHBEqGgS" role="3clFbG">
+            <node concept="2OqwBi" id="2tcGHBEqGgW" role="37vLTJ">
+              <node concept="Xjq3P" id="2tcGHBEqGgZ" role="2Oq$k0" />
+              <node concept="2OwXpG" id="2tcGHBEqGgV" role="2OqNvi">
+                <ref role="2Oxat5" node="2tcGHBEqGgM" resolve="sessionSolver" />
+              </node>
+            </node>
+            <node concept="37vLTw" id="2tcGHBEqGh0" role="37vLTx">
+              <ref role="3cqZAo" node="2tcGHBEqG6O" resolve="sessionSolver" />
+            </node>
+          </node>
+        </node>
       </node>
     </node>
     <node concept="2tJIrI" id="7eGEHDlcF7m" role="jymVt" />
@@ -6520,14 +6560,14 @@
       </node>
       <node concept="3Tm1VV" id="78CwJJcXwmn" role="1B3o_S" />
       <node concept="3clFbS" id="78CwJJcXwmp" role="3clF47">
-        <node concept="3clFbF" id="78CwJJcXxpO" role="3cqZAp">
-          <node concept="2OqwBi" id="78CwJJcXxqL" role="3clFbG">
-            <node concept="37vLTw" id="78CwJJcXxpN" role="2Oq$k0">
-              <ref role="3cqZAo" node="7eGEHDldhr$" resolve="registry" />
+        <node concept="3clFbF" id="2tcGHBEqHhq" role="3cqZAp">
+          <node concept="2OqwBi" id="2tcGHBEqHl4" role="3clFbG">
+            <node concept="37vLTw" id="2tcGHBEqHho" role="2Oq$k0">
+              <ref role="3cqZAo" node="2tcGHBEqGgM" resolve="sessionSolver" />
             </node>
-            <node concept="liA8E" id="78CwJJcXxuL" role="2OqNvi">
-              <ref role="37wK5l" node="7ISVfSJwqK" resolve="builtinSolver" />
-              <node concept="37vLTw" id="78CwJJcXC1v" role="37wK5m">
+            <node concept="liA8E" id="2tcGHBEqKQ8" role="2OqNvi">
+              <ref role="37wK5l" to="qrld:2tcGHBEqJAf" resolve="solverClass" />
+              <node concept="37vLTw" id="2tcGHBEqKT9" role="37wK5m">
                 <ref role="3cqZAo" node="78CwJJcXwmi" resolve="predicateSymbol" />
               </node>
             </node>
@@ -6565,6 +6605,7 @@
     <node concept="2tJIrI" id="78CwJJcTpyK" role="jymVt" />
     <node concept="3clFb_" id="7eGEHDlcF9o" role="jymVt">
       <property role="TrG5h" value="addRule" />
+      <property role="DiZV1" value="true" />
       <node concept="37vLTG" id="7eGEHDlcFbs" role="3clF46">
         <property role="TrG5h" value="rule" />
         <node concept="3uibUv" id="7eGEHDlcFct" role="1tU5fm">
@@ -6642,6 +6683,53 @@
       </node>
     </node>
     <node concept="2tJIrI" id="16gGH0VyPQh" role="jymVt" />
+    <node concept="3clFb_" id="2tcGHBDZ7NJ" role="jymVt">
+      <property role="TrG5h" value="addRules" />
+      <property role="1EzhhJ" value="false" />
+      <node concept="37vLTG" id="2tcGHBDZ7NK" role="3clF46">
+        <property role="TrG5h" value="rules" />
+        <node concept="3uibUv" id="2tcGHBDZ7NL" role="1tU5fm">
+          <ref role="3uigEE" to="33ny:~Collection" resolve="Collection" />
+          <node concept="3qUE_q" id="2tcGHBDZ7NM" role="11_B2D">
+            <node concept="3uibUv" id="2tcGHBDZ7NN" role="3qUE_r">
+              <ref role="3uigEE" to="i8dg:7eGEHDlc$9y" resolve="Rule" />
+            </node>
+          </node>
+        </node>
+      </node>
+      <node concept="3cqZAl" id="2tcGHBDZ7NO" role="3clF45" />
+      <node concept="3Tm1VV" id="2tcGHBDZ7NP" role="1B3o_S" />
+      <node concept="3uibUv" id="2tcGHBDZ7NR" role="Sfmx6">
+        <ref role="3uigEE" to="i8dg:7Oc59RS$wKP" resolve="InvalidRuleException" />
+      </node>
+      <node concept="3clFbS" id="2tcGHBDZ7NS" role="3clF47">
+        <node concept="1DcWWT" id="2tcGHBDZfxI" role="3cqZAp">
+          <node concept="3clFbS" id="2tcGHBDZfxK" role="2LFqv$">
+            <node concept="3clFbF" id="2tcGHBDZgvu" role="3cqZAp">
+              <node concept="1rXfSq" id="2tcGHBDZgvt" role="3clFbG">
+                <ref role="37wK5l" node="7eGEHDlcF9o" resolve="addRule" />
+                <node concept="37vLTw" id="2tcGHBDZg$A" role="37wK5m">
+                  <ref role="3cqZAo" node="2tcGHBDZfxM" resolve="rule" />
+                </node>
+              </node>
+            </node>
+          </node>
+          <node concept="3cpWsn" id="2tcGHBDZfxM" role="1Duv9x">
+            <property role="TrG5h" value="rule" />
+            <node concept="3uibUv" id="2tcGHBDZfCH" role="1tU5fm">
+              <ref role="3uigEE" to="i8dg:7eGEHDlc$9y" resolve="Rule" />
+            </node>
+          </node>
+          <node concept="37vLTw" id="2tcGHBDZfxS" role="1DdaDG">
+            <ref role="3cqZAo" node="2tcGHBDZ7NK" resolve="rules" />
+          </node>
+        </node>
+      </node>
+      <node concept="2AHcQZ" id="2tcGHBDZ9Jp" role="2AJF6D">
+        <ref role="2AI5Lk" to="wyt6:~Override" resolve="Override" />
+      </node>
+    </node>
+    <node concept="2tJIrI" id="2tcGHBDZ8MQ" role="jymVt" />
     <node concept="3clFb_" id="16gGH0Vz2Uo" role="jymVt">
       <property role="TrG5h" value="name" />
       <node concept="17QB3L" id="16gGH0Vz6sJ" role="3clF45" />
@@ -6703,33 +6791,6 @@
       </node>
     </node>
     <node concept="2tJIrI" id="2$F5QpusKcO" role="jymVt" />
-    <node concept="3clFb_" id="2$F5QpusKcG" role="jymVt">
-      <property role="TrG5h" value="headVariables" />
-      <node concept="3uibUv" id="2$F5QpusKcH" role="3clF45">
-        <ref role="3uigEE" to="33ny:~Set" resolve="Set" />
-        <node concept="3uibUv" id="2$F5QpusKcI" role="11_B2D">
-          <ref role="3uigEE" to="45ys:1mP5b6jQP$C" resolve="ILogical" />
-        </node>
-      </node>
-      <node concept="3Tm1VV" id="2$F5QpusKcJ" role="1B3o_S" />
-      <node concept="3clFbS" id="2$F5QpusKcK" role="3clF47">
-        <node concept="3clFbF" id="2$F5QpusKcL" role="3cqZAp">
-          <node concept="2YIFZM" id="2$F5QpusKcM" role="3clFbG">
-            <ref role="37wK5l" to="33ny:~Collections.unmodifiableSet(java.util.Set):java.util.Set" resolve="unmodifiableSet" />
-            <ref role="1Pybhc" to="33ny:~Collections" resolve="Collections" />
-            <node concept="2OqwBi" id="2$F5QpuudXP" role="37wK5m">
-              <node concept="37vLTw" id="2$F5QpusLoM" role="2Oq$k0">
-                <ref role="3cqZAo" node="2$F5QpusuSB" resolve="headVar2Rule" />
-              </node>
-              <node concept="liA8E" id="2$F5Qpuue8r" role="2OqNvi">
-                <ref role="37wK5l" to="33ny:~Map.keySet():java.util.Set" resolve="keySet" />
-              </node>
-            </node>
-          </node>
-        </node>
-      </node>
-    </node>
-    <node concept="2tJIrI" id="2$F5Qpuuecl" role="jymVt" />
     <node concept="3clFb_" id="2$F5QpuufjQ" role="jymVt">
       <property role="TrG5h" value="declaringRule" />
       <node concept="37vLTG" id="2$F5QpuuhMO" role="3clF46">
@@ -7608,6 +7669,13 @@
     <node concept="3uibUv" id="78CwJJcTnG5" role="1zkMxy">
       <ref role="3uigEE" to="rchb:5uFPQ7BvNzE" resolve="PlanningSession" />
     </node>
+    <node concept="312cEg" id="2tcGHBEqGgM" role="jymVt">
+      <property role="TrG5h" value="sessionSolver" />
+      <node concept="3Tm6S6" id="2tcGHBEqGgN" role="1B3o_S" />
+      <node concept="3uibUv" id="2tcGHBEqGgP" role="1tU5fm">
+        <ref role="3uigEE" to="qrld:6Kcfpq7B0b0" resolve="SessionSolver" />
+      </node>
+    </node>
   </node>
   <node concept="312cEu" id="7eGEHDldgwf">
     <property role="TrG5h" value="ConstraintRegistry" />
@@ -7629,7 +7697,7 @@
             <ref role="1Pybhc" to="33ny:~Collections" resolve="Collections" />
             <node concept="2OqwBi" id="78CwJJcXKov" role="37wK5m">
               <node concept="37vLTw" id="78CwJJcXKow" role="2Oq$k0">
-                <ref role="3cqZAo" node="7eGEHDley5W" resolve="userConstraintArgTypes" />
+                <ref role="3cqZAo" node="7eGEHDley5W" resolve="constraintArgTypes" />
               </node>
               <node concept="liA8E" id="78CwJJcXKox" role="2OqNvi">
                 <ref role="37wK5l" to="33ny:~Map.keySet():java.util.Set" resolve="keySet" />
@@ -7657,7 +7725,7 @@
             <ref role="1Pybhc" to="33ny:~Collections" resolve="Collections" />
             <node concept="2OqwBi" id="78CwJJcXo6Q" role="37wK5m">
               <node concept="37vLTw" id="78CwJJcXo2d" role="2Oq$k0">
-                <ref role="3cqZAo" node="7eGEHDley5W" resolve="userConstraintArgTypes" />
+                <ref role="3cqZAo" node="7eGEHDley5W" resolve="constraintArgTypes" />
               </node>
               <node concept="liA8E" id="78CwJJcXofr" role="2OqNvi">
                 <ref role="37wK5l" to="33ny:~Map.get(java.lang.Object):java.lang.Object" resolve="get" />
@@ -7691,53 +7759,14 @@
           <node concept="2YIFZM" id="ZqZbw4RKXF" role="3clFbG">
             <ref role="37wK5l" to="33ny:~Collections.unmodifiableSet(java.util.Set):java.util.Set" resolve="unmodifiableSet" />
             <ref role="1Pybhc" to="33ny:~Collections" resolve="Collections" />
-            <node concept="2OqwBi" id="ZqZbw4RLsb" role="37wK5m">
-              <node concept="37vLTw" id="78CwJJcXRtE" role="2Oq$k0">
-                <ref role="3cqZAo" node="7ISVfSJtsW" resolve="builtinSolvers" />
-              </node>
-              <node concept="liA8E" id="ZqZbw4RLHg" role="2OqNvi">
-                <ref role="37wK5l" to="33ny:~Map.keySet():java.util.Set" resolve="keySet" />
-              </node>
+            <node concept="37vLTw" id="78CwJJcXRtE" role="37wK5m">
+              <ref role="3cqZAo" node="7ISVfSJtsW" resolve="solvers" />
             </node>
           </node>
         </node>
       </node>
     </node>
     <node concept="2tJIrI" id="78CwJJcXbSO" role="jymVt" />
-    <node concept="3clFb_" id="7ISVfSJwqK" role="jymVt">
-      <property role="TrG5h" value="builtinSolver" />
-      <node concept="37vLTG" id="78CwJJcX_LG" role="3clF46">
-        <property role="TrG5h" value="predicateSymbol" />
-        <node concept="3uibUv" id="78CwJJcXAn8" role="1tU5fm">
-          <ref role="3uigEE" to="qrld:5uFPQ7B$$3f" resolve="PredicateSymbol" />
-        </node>
-      </node>
-      <node concept="3Tm1VV" id="7ISVfSJwqN" role="1B3o_S" />
-      <node concept="3clFbS" id="7ISVfSJwqO" role="3clF47">
-        <node concept="3clFbF" id="78CwJJcXAoP" role="3cqZAp">
-          <node concept="2OqwBi" id="78CwJJcXAtZ" role="3clFbG">
-            <node concept="37vLTw" id="78CwJJcXAoO" role="2Oq$k0">
-              <ref role="3cqZAo" node="7ISVfSJtsW" resolve="builtinSolvers" />
-            </node>
-            <node concept="liA8E" id="78CwJJcXAKS" role="2OqNvi">
-              <ref role="37wK5l" to="33ny:~Map.get(java.lang.Object):java.lang.Object" resolve="get" />
-              <node concept="37vLTw" id="78CwJJcXAQs" role="37wK5m">
-                <ref role="3cqZAo" node="78CwJJcX_LG" resolve="predicateSymbol" />
-              </node>
-            </node>
-          </node>
-        </node>
-      </node>
-      <node concept="3uibUv" id="7ISVfSJzEP" role="3clF45">
-        <ref role="3uigEE" to="wyt6:~Class" resolve="Class" />
-        <node concept="3qUE_q" id="7ISVfSJzGm" role="11_B2D">
-          <node concept="3uibUv" id="7ISVfSJzHu" role="3qUE_r">
-            <ref role="3uigEE" to="qrld:6Kcfpq7AYBh" resolve="Queryable" />
-          </node>
-        </node>
-      </node>
-    </node>
-    <node concept="2tJIrI" id="2pvEdquvpGe" role="jymVt" />
     <node concept="3clFb_" id="7eGEHDldpbj" role="jymVt">
       <property role="TrG5h" value="checkValidConstraint" />
       <node concept="3cqZAl" id="7Oc59RSHNKF" role="3clF45" />
@@ -7875,7 +7904,7 @@
                         <ref role="37wK5l" to="33ny:~List.equals(java.lang.Object):boolean" resolve="equals" />
                         <node concept="2OqwBi" id="30XHGaP5H3s" role="37wK5m">
                           <node concept="37vLTw" id="30XHGaP5H3t" role="2Oq$k0">
-                            <ref role="3cqZAo" node="7eGEHDley5W" resolve="userConstraintArgTypes" />
+                            <ref role="3cqZAo" node="7eGEHDley5W" resolve="constraintArgTypes" />
                           </node>
                           <node concept="liA8E" id="30XHGaP5H3u" role="2OqNvi">
                             <ref role="37wK5l" to="33ny:~Map.get(java.lang.Object):java.lang.Object" resolve="get" />
@@ -7896,7 +7925,7 @@
               </node>
               <node concept="2OqwBi" id="7eGEHDleL6q" role="3clFbw">
                 <node concept="37vLTw" id="7eGEHDleIbQ" role="2Oq$k0">
-                  <ref role="3cqZAo" node="7eGEHDley5W" resolve="userConstraintArgTypes" />
+                  <ref role="3cqZAo" node="7eGEHDley5W" resolve="constraintArgTypes" />
                 </node>
                 <node concept="liA8E" id="7eGEHDleLnR" role="2OqNvi">
                   <ref role="37wK5l" to="33ny:~Map.containsKey(java.lang.Object):boolean" resolve="containsKey" />
@@ -8108,7 +8137,7 @@
             <node concept="3clFbF" id="7eGEHDleQCQ" role="3cqZAp">
               <node concept="2OqwBi" id="7eGEHDleQIf" role="3clFbG">
                 <node concept="37vLTw" id="7eGEHDleQCP" role="2Oq$k0">
-                  <ref role="3cqZAo" node="7eGEHDley5W" resolve="userConstraintArgTypes" />
+                  <ref role="3cqZAo" node="7eGEHDley5W" resolve="constraintArgTypes" />
                 </node>
                 <node concept="liA8E" id="7eGEHDleQZ$" role="2OqNvi">
                   <ref role="37wK5l" to="33ny:~Map.put(java.lang.Object,java.lang.Object):java.lang.Object" resolve="put" />
@@ -8131,92 +8160,6 @@
                 </node>
               </node>
             </node>
-            <node concept="3cpWs8" id="78CwJJcX8LU" role="3cqZAp">
-              <node concept="3cpWsn" id="78CwJJcX8LV" role="3cpWs9">
-                <property role="TrG5h" value="list" />
-                <node concept="3uibUv" id="78CwJJcX8LN" role="1tU5fm">
-                  <ref role="3uigEE" to="33ny:~List" resolve="List" />
-                  <node concept="3uibUv" id="78CwJJcX8LQ" role="11_B2D">
-                    <ref role="3uigEE" to="qrld:6Kcfpq7BfEn" resolve="Constraint" />
-                  </node>
-                </node>
-                <node concept="2OqwBi" id="78CwJJcX8LW" role="33vP2m">
-                  <node concept="37vLTw" id="78CwJJcX8LX" role="2Oq$k0">
-                    <ref role="3cqZAo" node="78CwJJcX66W" resolve="constraints" />
-                  </node>
-                  <node concept="liA8E" id="78CwJJcX8LY" role="2OqNvi">
-                    <ref role="37wK5l" to="33ny:~Map.get(java.lang.Object):java.lang.Object" resolve="get" />
-                    <node concept="2OqwBi" id="78CwJJcX8LZ" role="37wK5m">
-                      <node concept="37vLTw" id="78CwJJcX8M0" role="2Oq$k0">
-                        <ref role="3cqZAo" node="5uFPQ7BH1yJ" resolve="cst" />
-                      </node>
-                      <node concept="liA8E" id="78CwJJcX8M1" role="2OqNvi">
-                        <ref role="37wK5l" to="qrld:5uFPQ7B_aTC" resolve="symbol" />
-                      </node>
-                    </node>
-                  </node>
-                </node>
-              </node>
-            </node>
-            <node concept="3clFbJ" id="78CwJJcX9b8" role="3cqZAp">
-              <node concept="3clFbS" id="78CwJJcX9ba" role="3clFbx">
-                <node concept="3clFbF" id="78CwJJcX9sx" role="3cqZAp">
-                  <node concept="37vLTI" id="78CwJJcX9vS" role="3clFbG">
-                    <node concept="2ShNRf" id="78CwJJcX9wY" role="37vLTx">
-                      <node concept="1pGfFk" id="78CwJJcX9MW" role="2ShVmc">
-                        <ref role="37wK5l" to="33ny:~ArrayList.&lt;init&gt;()" resolve="ArrayList" />
-                        <node concept="3uibUv" id="78CwJJcX9SU" role="1pMfVU">
-                          <ref role="3uigEE" to="qrld:6Kcfpq7BfEn" resolve="Constraint" />
-                        </node>
-                      </node>
-                    </node>
-                    <node concept="37vLTw" id="78CwJJcX9sv" role="37vLTJ">
-                      <ref role="3cqZAo" node="78CwJJcX8LV" resolve="list" />
-                    </node>
-                  </node>
-                </node>
-                <node concept="3clFbF" id="78CwJJcX9X4" role="3cqZAp">
-                  <node concept="2OqwBi" id="78CwJJcX9ZE" role="3clFbG">
-                    <node concept="37vLTw" id="78CwJJcX9X2" role="2Oq$k0">
-                      <ref role="3cqZAo" node="78CwJJcX66W" resolve="constraints" />
-                    </node>
-                    <node concept="liA8E" id="78CwJJcXa5R" role="2OqNvi">
-                      <ref role="37wK5l" to="33ny:~Map.put(java.lang.Object,java.lang.Object):java.lang.Object" resolve="put" />
-                      <node concept="2OqwBi" id="78CwJJcXaec" role="37wK5m">
-                        <node concept="37vLTw" id="78CwJJcXabz" role="2Oq$k0">
-                          <ref role="3cqZAo" node="5uFPQ7BH1yJ" resolve="cst" />
-                        </node>
-                        <node concept="liA8E" id="78CwJJcXain" role="2OqNvi">
-                          <ref role="37wK5l" to="qrld:5uFPQ7B_aTC" resolve="symbol" />
-                        </node>
-                      </node>
-                      <node concept="37vLTw" id="78CwJJcXar3" role="37wK5m">
-                        <ref role="3cqZAo" node="78CwJJcX8LV" resolve="list" />
-                      </node>
-                    </node>
-                  </node>
-                </node>
-              </node>
-              <node concept="3clFbC" id="78CwJJcX9qk" role="3clFbw">
-                <node concept="10Nm6u" id="78CwJJcX9rk" role="3uHU7w" />
-                <node concept="37vLTw" id="78CwJJcX9lH" role="3uHU7B">
-                  <ref role="3cqZAo" node="78CwJJcX8LV" resolve="list" />
-                </node>
-              </node>
-            </node>
-            <node concept="3clFbF" id="78CwJJcX71$" role="3cqZAp">
-              <node concept="2OqwBi" id="78CwJJcXazH" role="3clFbG">
-                <node concept="37vLTw" id="78CwJJcX8M2" role="2Oq$k0">
-                  <ref role="3cqZAo" node="78CwJJcX8LV" resolve="list" />
-                </node>
-                <node concept="liA8E" id="78CwJJcXaHw" role="2OqNvi">
-                  <ref role="37wK5l" to="33ny:~List.add(java.lang.Object):boolean" resolve="add" />
-                  <node concept="37vLTw" id="78CwJJcXaJG" role="37wK5m">
-                    <ref role="3cqZAo" node="5uFPQ7BH1yJ" resolve="cst" />
-                  </node>
-                </node>
-              </node>
-            </node>
             <node concept="3clFbH" id="78CwJJcXaLt" role="3cqZAp" />
           </node>
           <node concept="2ZW3vV" id="5uFPQ7BH0Nf" role="3clFbw">
@@ -8256,10 +8199,10 @@
               <node concept="3clFbF" id="7ISVfSJv16" role="3cqZAp">
                 <node concept="2OqwBi" id="7ISVfSJvhy" role="3clFbG">
                   <node concept="37vLTw" id="7ISVfSJv14" role="2Oq$k0">
-                    <ref role="3cqZAo" node="7ISVfSJtsW" resolve="builtinSolvers" />
+                    <ref role="3cqZAo" node="7ISVfSJtsW" resolve="solvers" />
                   </node>
                   <node concept="liA8E" id="7ISVfSJvtA" role="2OqNvi">
-                    <ref role="37wK5l" to="33ny:~Map.put(java.lang.Object,java.lang.Object):java.lang.Object" resolve="put" />
+                    <ref role="37wK5l" to="33ny:~Set.add(java.lang.Object):boolean" resolve="add" />
                     <node concept="2OqwBi" id="78CwJJcX$kh" role="37wK5m">
                       <node concept="37vLTw" id="78CwJJcX$fr" role="2Oq$k0">
                         <ref role="3cqZAo" node="5uFPQ7BH2qT" resolve="pred" />
@@ -8268,14 +8211,6 @@
                         <ref role="37wK5l" to="qrld:6Kcfpq7Bjgi" resolve="symbol" />
                       </node>
                     </node>
-                    <node concept="2OqwBi" id="7ISVfSJvB5" role="37wK5m">
-                      <node concept="37vLTw" id="7ISVfSJvyy" role="2Oq$k0">
-                        <ref role="3cqZAo" node="5uFPQ7BH2qT" resolve="pred" />
-                      </node>
-                      <node concept="liA8E" id="7ISVfSJw6g" role="2OqNvi">
-                        <ref role="37wK5l" to="qrld:4xBopTzlOsG" resolve="solverClass" />
-                      </node>
-                    </node>
                   </node>
                 </node>
               </node>
@@ -8322,42 +8257,26 @@
     <node concept="2tJIrI" id="1zN1RIlmLd2" role="jymVt" />
     <node concept="2tJIrI" id="2pvEdquu$2W" role="jymVt" />
     <node concept="312cEg" id="7ISVfSJtsW" role="jymVt">
-      <property role="TrG5h" value="builtinSolvers" />
+      <property role="TrG5h" value="solvers" />
       <node concept="3Tm6S6" id="7ISVfSJtsX" role="1B3o_S" />
       <node concept="3uibUv" id="7ISVfSJtsY" role="1tU5fm">
-        <ref role="3uigEE" to="33ny:~Map" resolve="Map" />
+        <ref role="3uigEE" to="33ny:~Set" resolve="Set" />
         <node concept="3uibUv" id="78CwJJcXzcn" role="11_B2D">
           <ref role="3uigEE" to="qrld:5uFPQ7B$$3f" resolve="PredicateSymbol" />
         </node>
-        <node concept="3uibUv" id="7ISVfSJuB_" role="11_B2D">
-          <ref role="3uigEE" to="wyt6:~Class" resolve="Class" />
-          <node concept="3qUE_q" id="7ISVfSJuGO" role="11_B2D">
-            <node concept="3uibUv" id="7ISVfSJuJL" role="3qUE_r">
-              <ref role="3uigEE" to="qrld:6Kcfpq7AYBh" resolve="Queryable" />
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-          </node>
-        </node>
       </node>
       <node concept="2ShNRf" id="7ISVfSJtt0" role="33vP2m">
         <node concept="1pGfFk" id="7ISVfSJtt1" role="2ShVmc">
-          <ref role="37wK5l" to="33ny:~HashMap.&lt;init&gt;()" resolve="HashMap" />
+          <ref role="37wK5l" to="33ny:~HashSet.&lt;init&gt;()" resolve="HashSet" />
           <node concept="3uibUv" id="78CwJJcXzNm" role="1pMfVU">
             <ref role="3uigEE" to="qrld:5uFPQ7B$$3f" resolve="PredicateSymbol" />
           </node>
-          <node concept="3uibUv" id="7ISVfSJuMt" role="1pMfVU">
-            <ref role="3uigEE" to="wyt6:~Class" resolve="Class" />
-            <node concept="3qUE_q" id="7ISVfSJuMu" role="11_B2D">
-              <node concept="3uibUv" id="7ISVfSJuMv" role="3qUE_r">
-                <ref role="3uigEE" to="qrld:6Kcfpq7AYBh" resolve="Queryable" />
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         </node>
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     </node>
     <node concept="2tJIrI" id="2pvEdquuHIN" role="jymVt" />
     <node concept="312cEg" id="7eGEHDley5W" role="jymVt">
-      <property role="TrG5h" value="userConstraintArgTypes" />
+      <property role="TrG5h" value="constraintArgTypes" />
       <node concept="3Tm6S6" id="7eGEHDley5X" role="1B3o_S" />
       <node concept="3uibUv" id="7eGEHDley91" role="1tU5fm">
         <ref role="3uigEE" to="33ny:~Map" resolve="Map" />
@@ -8389,36 +8308,6 @@
       </node>
     </node>
     <node concept="2tJIrI" id="78CwJJcX5vW" role="jymVt" />
-    <node concept="312cEg" id="78CwJJcX66W" role="jymVt">
-      <property role="TrG5h" value="constraints" />
-      <node concept="3Tm6S6" id="78CwJJcX66X" role="1B3o_S" />
-      <node concept="2ShNRf" id="78CwJJcX6Hi" role="33vP2m">
-        <node concept="1pGfFk" id="78CwJJcX7WH" role="2ShVmc">
-          <ref role="37wK5l" to="33ny:~HashMap.&lt;init&gt;()" resolve="HashMap" />
-          <node concept="3uibUv" id="78CwJJcX88o" role="1pMfVU">
-            <ref role="3uigEE" to="qrld:54i3FxcZHHF" resolve="ConstraintSymbol" />
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-          <node concept="3uibUv" id="78CwJJcX8gL" role="1pMfVU">
-            <ref role="3uigEE" to="33ny:~List" resolve="List" />
-            <node concept="3uibUv" id="78CwJJcX8m6" role="11_B2D">
-              <ref role="3uigEE" to="qrld:6Kcfpq7BfEn" resolve="Constraint" />
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-          </node>
-        </node>
-      </node>
-      <node concept="3uibUv" id="78CwJJcX7zv" role="1tU5fm">
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-        <node concept="3uibUv" id="78CwJJcX7_D" role="11_B2D">
-          <ref role="3uigEE" to="qrld:54i3FxcZHHF" resolve="ConstraintSymbol" />
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-        <node concept="3uibUv" id="78CwJJcX6Ex" role="11_B2D">
-          <ref role="3uigEE" to="33ny:~List" resolve="List" />
-          <node concept="3uibUv" id="78CwJJcX6F_" role="11_B2D">
-            <ref role="3uigEE" to="qrld:6Kcfpq7BfEn" resolve="Constraint" />
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-        </node>
-      </node>
-    </node>
   </node>
 </model>