public IInferenceResult Ask(FOLKnowledgeBase KB, ISentence alpha)
{
ISet<Clause> sos = new HashedSet<Clause>();
ISet<Clause> usable = new HashedSet<Clause>();
// Usable set will be the set of clauses in the KB,
// are assuming this is satisfiable as using the
// ISet of Support strategy.
//foreach (var standardizedC in KB.GetAllClauses().Select(c => KB.StandardizeApart(c)))
foreach (var standardizedC in KB.GetAllClauses())
{
standardizedC.SetStandardizedApartCheckNotRequired();
usable.UnionWith(standardizedC.GetFactors());
}
// Ensure reflexivity axiom is added to usable if using paramodulation.
if (this.UseParamodulation)
{
// Reflexivity Axiom: x = x
var reflexivityAxiom = new TermEquality(new Variable("x"), new Variable("x"));
var reflexivityClause = new Clause();
reflexivityClause.AddLiteral(new Literal(reflexivityAxiom));
reflexivityClause = KB.StandardizeApart(reflexivityClause);
reflexivityClause.SetStandardizedApartCheckNotRequired();
usable.Add(reflexivityClause);
}
ISentence notAlpha = new NotSentence(alpha);
// Want to use an answer literal to pull
// query variables where necessary
var answerLiteral = KB.CreateAnswerLiteral(notAlpha);
var answerLiteralVariables = KB
.CollectAllVariables(answerLiteral.AtomicSentence);
var answerClause = new Clause();
if (answerLiteralVariables.Count > 0) {
ISentence notAlphaWithAnswer = new ConnectedSentence(Connectors.Or,
notAlpha, answerLiteral.AtomicSentence);
// foreach (var standardizedC in
// KB.ConvertToClauses(notAlphaWithAnswer).Select(KB.StandardizeApart))
foreach (var standardizedC in
KB.ConvertToClauses(notAlphaWithAnswer))
{
Clause c = KB.StandardizeApart(standardizedC);
c.SetProofStep(new ProofStepGoal(c));
c.SetStandardizedApartCheckNotRequired();
sos.UnionWith(c.GetFactors());
}
answerClause.AddLiteral(answerLiteral);
}
else
{
//foreach (var standardizedC in
// KB.ConvertToClauses(notAlpha).Select(KB.StandardizeApart))
foreach (var standardizedC in
KB.ConvertToClauses(notAlpha))
{
Clause c = KB.StandardizeApart(standardizedC);
c.SetProofStep(new ProofStepGoal(c));
c.SetStandardizedApartCheckNotRequired();
sos.UnionWith(standardizedC.GetFactors());
}
}
// Ensure all subsumed clauses are removed
usable.ExceptWith(SubsumptionElimination.FindSubsumedClauses(usable));
sos.ExceptWith(SubsumptionElimination.FindSubsumedClauses(sos));
var ansHandler = new OTTERAnswerHandler(answerLiteral,
answerLiteralVariables, answerClause, this.MaxQueryTime);
var idxdClauses = new IndexedClauses(LightestClauseHeuristic, sos, usable);
return this.Otter(ansHandler, idxdClauses, sos, usable);
}