For this several notions are introduced.
Logical variable is called "principal" if it is used in principal
occurrences and at some point during evaluation is unified or bound.
Principal occurrence is called "volatile" if it uses principal logicals.
PrincipalObserverDispatcher's task is to track volatile occurrences
by enabling uni observers on all free logicals in principal occ-s.
RewindVolatileOccurrencesStage then on events of incremental usage
of volatile occurrences (e.g. match on it, or continued activation)
resets journal cursor to the position of initial occurrence activation,
where it can be re-evaluated with fresh, unaffected, logicals.
It's the only stage that goes backwards in journal.
So in this way unification is incrementally cancelled.
link to MPSCR-62 (docs)
Rename NonIncrementalProcessing -> DefaultProcessing
Add GroundProcessing as common superclass to handle OccurrenceContractObserver
Add another test for this occurrence contract logic.
Allows to carry logically connected information in one object.
Needed for subsequent changes to ConstraintOccurrence, which
must have better information on source rule: rule template name.
Used by occurrence cache.
The test substructuralTS_indirectResourceDependency is not doing what it's intended
to be doing b/c of apparenly wrongly understood contract of the `also()` method.
It is not supposed to pass the result of the computation to the "chained" method.
Compare `T.also(block: (T) -> Unit): T` and `T.let(block: (T) -> R): R`.
After having fixed the code, the test no longer passes.
Instead of simple allowed/not option sometimes Unsafe
is useful. 'Unsafe' status may be present when there're
few "bad" rules.
With this level end code may resolve to go with
incrementality without strict guarantees.
Now Evidence isn't unique for each Chunk: Occurrence Chunks fully
share evidence and justifications with their activating match.
So, less collections of justifications are created, approx. 2 times less.
Invariant ensures that retroactively added justifications
(added on past parent chunk, see fix commit) are propagated
for all relevant children of justified parent chunk.
Make Occurrence a Justified entity and drop .justifications() from
ConstraintOccurrence.java because justifications are used only internally.
A single justification is now called Evidence (typealias to Int),
so Justified entities are justified by Evidence-s.
Introduce Supervisor, extract evaluation-related stuff from Program, merge with EvaluationFeedbackHandler.
Move implementation of EvaluationFeedback to internal API, reduce number of public interfaces.
Cleaner interface for reporting feedback.
Fedor Isakov