Package org.projog.core.predicate.builtin.kb

Class Inspect.InspectPredicate

  • All Implemented Interfaces:
    Predicate
    Enclosing class:
    Inspect
    private final class Inspect.InspectPredicate
extends java.lang.Object
implements Predicate

    • Field Detail

      • clauseHead

        private final Term clauseHead

      • clauseBody

        private final Term clauseBody

      • implications

        private final java.util.Iterator<ClauseModel> implications

    • Constructor Detail

      • InspectPredicate

        private InspectPredicate​(Term clauseHead,
                         Term clauseBody,
                         java.util.Iterator<ClauseModel> implications)

    • Method Detail

      • evaluate

        public boolean evaluate()
        Description copied from interface: Predicate
        Attempts to satisfy the goal this instance represents.

        Calling this method multiple times on a single instance allows all possible answers to be identified. An attempt to find a solution carries on from where the last successful call finished.

        If PredicateFactory.isRetryable() returns false then this method should only be called once per individual query (no attempt should be made to find alternative solutions).

        If PredicateFactory.isRetryable() returns true then, in order to find all possible solutions for an individual query, this method should be recalled on backtracking until it returns false.

        Specified by:
        evaluate in interface Predicate
        Returns:
        true if there is a rule in the knowledge base whose consequent can be unified with clauseHead and, if clauseBody is not null, whose antecedent can be unified with clauseBody.
        See Also:
        PredicateFactory.getPredicate(Term[])

      • remove

        private void remove()

      • backtrack

        private void backtrack​(Term clauseHead,
                       Term clauseBody)

      • unifiable

        private boolean unifiable​(Term clauseHead,
                          Term clauseBody,
                          ClauseModel clauseModel)

      • couldReevaluationSucceed

        public boolean couldReevaluationSucceed()
        Description copied from interface: Predicate
        Could the next re-evaluation of this instance succeed?

        Specifies whether a specific instance of a specific implementation of Predicate, that has already had Predicate.evaluate() called on it at least once, could possibly return true the next time Predicate.evaluate() is called on it. i.e. is it worth trying to continue to find solutions for the specific query this particular instance represents and has been evaluating?

        (Note: the difference between this method and PredicateFactory.isRetryable() is that PredicateFactory.isRetryable() deals with whether, in general, a specific implementation (rather than instance) of Predicate could ever produce multiple answers for an individual query.)

        Specified by:
        couldReevaluationSucceed in interface Predicate
        Returns:
        true if an attempt to re-evaluate this instance could possible succeed, false otherwise