//
// START-InferenceProcedure
public InferenceResult ask(FOLKnowledgeBase kb, Sentence aQuery)
{
//
// Get the background knowledge - are assuming this is satisfiable
// as using Set of Support strategy.
List <Clause> bgClauses = new List <Clause>(kb.getAllClauses());
List <Clause> removeList = SubsumptionElimination.findSubsumedClauses(bgClauses);
foreach (Clause c in removeList)
{
bgClauses.Remove(c);
}
List <Chain> background = createChainsFromClauses(bgClauses);
// Collect the information necessary for constructing
// an answer (supports use of answer literals).
AnswerHandler ansHandler = new AnswerHandler(kb, aQuery, maxQueryTime, this);
IndexedFarParents ifps = new IndexedFarParents(ansHandler
.getSetOfSupport(), background);
// Iterative deepening to be used
for (int maxDepth = 1; maxDepth < int.MaxValue; maxDepth++)
{
// Track the depth actually reached
ansHandler.resetMaxDepthReached();
if (null != tracer)
{
tracer.reset();
}
foreach (Chain nearParent in ansHandler.getSetOfSupport())
{
recursiveDLS(maxDepth, 0, nearParent, ifps, ansHandler);
if (ansHandler.isComplete())
{
return(ansHandler);
}
}
// This means the search tree
// has bottomed out (i.e. finite).
// Return what I know based on exploring everything.
if (ansHandler.getMaxDepthReached() < maxDepth)
{
return(ansHandler);
}
}
return(ansHandler);
}
// START-InferenceProcedure
public InferenceResult ask(FOLKnowledgeBase KB, Sentence alpha)
{
List <Clause> sos = new List <Clause>();
List <Clause> usable = new List <Clause>();
// Usable set will be the set of clauses in the KB,
// are assuming this is satisfiable as using the
// Set of Support strategy.
foreach (Clause c in KB.getAllClauses())
{
Clause c2 = KB.standardizeApart(c);
c2.setStandardizedApartCheckNotRequired();
usable.AddRange(c2.getFactors());
}
// Ensure reflexivity axiom is added to usable if using paramodulation.
if (isUseParamodulation())
{
// Reflexivity Axiom: x = x
TermEquality reflexivityAxiom = new TermEquality(new Variable("x"),
new Variable("x"));
Clause reflexivityClause = new Clause();
reflexivityClause.addLiteral(new Literal(reflexivityAxiom));
reflexivityClause = KB.standardizeApart(reflexivityClause);
reflexivityClause.setStandardizedApartCheckNotRequired();
usable.Add(reflexivityClause);
}
Sentence notAlpha = new NotSentence(alpha);
// Want to use an answer literal to pull
// query variables where necessary
Literal answerLiteral = KB.createAnswerLiteral(notAlpha);
List <Variable> answerLiteralVariables = KB
.collectAllVariables(answerLiteral.getAtomicSentence());
Clause answerClause = new Clause();
if (answerLiteralVariables.Count > 0)
{
Sentence notAlphaWithAnswer = new ConnectedSentence(Connectors.OR,
notAlpha, answerLiteral.getAtomicSentence());
foreach (Clause c in KB.convertToClauses(notAlphaWithAnswer))
{
Clause c2 = KB.standardizeApart(c);
c2.setProofStep(new ProofStepGoal(c2));
c2.setStandardizedApartCheckNotRequired();
sos.AddRange(c2.getFactors());
}
answerClause.addLiteral(answerLiteral);
}
else
{
foreach (Clause c in KB.convertToClauses(notAlpha))
{
Clause c2 = KB.standardizeApart(c);
c2.setProofStep(new ProofStepGoal(c2));
c2.setStandardizedApartCheckNotRequired();
sos.AddRange(c2.getFactors());
}
}
// Ensure all subsumed clauses are removed
foreach (Clause c in SubsumptionElimination.findSubsumedClauses(usable))
{
usable.Remove(c);
}
foreach (Clause c in SubsumptionElimination.findSubsumedClauses(sos))
{
sos.Remove(c);
}
OTTERAnswerHandler ansHandler = new OTTERAnswerHandler(answerLiteral,
answerLiteralVariables, answerClause, maxQueryTime);
IndexedClauses idxdClauses = new IndexedClauses(
getLightestClauseHeuristic(), sos, usable);
return(otter(ansHandler, idxdClauses, sos, usable));
}
//
// START-InferenceProcedure
public InferenceResult ask(FOLKnowledgeBase KB, Sentence alpha)
{
// clauses <- the set of clauses in CNF representation of KB ^ ~alpha
ISet <Clause> clauses = CollectionFactory.CreateSet <Clause>();
foreach (Clause cIter in KB.getAllClauses())
{
Clause c = cIter;
c = KB.standardizeApart(c);
c.setStandardizedApartCheckNotRequired();
clauses.AddAll(c.getFactors());
}
Sentence notAlpha = new NotSentence(alpha);
// Want to use an answer literal to pull
// query variables where necessary
Literal answerLiteral = KB.createAnswerLiteral(notAlpha);
ISet <Variable> answerLiteralVariables = KB.collectAllVariables(answerLiteral.getAtomicSentence());
Clause answerClause = new Clause();
if (answerLiteralVariables.Size() > 0)
{
Sentence notAlphaWithAnswer = new ConnectedSentence(Connectors.OR,
notAlpha, answerLiteral.getAtomicSentence());
foreach (Clause cIter in KB.convertToClauses(notAlphaWithAnswer))
{
Clause c = cIter;
c = KB.standardizeApart(c);
c.setProofStep(new ProofStepGoal(c));
c.setStandardizedApartCheckNotRequired();
clauses.AddAll(c.getFactors());
}
answerClause.addLiteral(answerLiteral);
}
else
{
foreach (Clause cIter in KB.convertToClauses(notAlpha))
{
Clause c = cIter;
c = KB.standardizeApart(c);
c.setProofStep(new ProofStepGoal(c));
c.setStandardizedApartCheckNotRequired();
clauses.AddAll(c.getFactors());
}
}
TFMAnswerHandler ansHandler = new TFMAnswerHandler(answerLiteral,
answerLiteralVariables, answerClause, maxQueryTime);
// new <- {}
ISet <Clause> newClauses = CollectionFactory.CreateSet <Clause>();
ISet <Clause> toAdd = CollectionFactory.CreateSet <Clause>();
// loop do
int noOfPrevClauses = clauses.Size();
do
{
if (null != tracer)
{
tracer.stepStartWhile(clauses, clauses.Size(), newClauses.Size());
}
newClauses.Clear();
// for each Ci, Cj in clauses do
Clause[] clausesA = clauses.ToArray();
// Basically, using the simple T)wo F)inger M)ethod here.
for (int i = 0; i < clausesA.Length; i++)
{
Clause cI = clausesA[i];
if (null != tracer)
{
tracer.stepOuterFor(cI);
}
for (int j = i; j < clausesA.Length; j++)
{
Clause cJ = clausesA[j];
if (null != tracer)
{
tracer.stepInnerFor(cI, cJ);
}
// resolvent <- FOL-RESOLVE(Ci, Cj)
ISet <Clause> resolvents = cI.binaryResolvents(cJ);
if (resolvents.Size() > 0)
{
toAdd.Clear();
// new <- new <UNION> resolvent
foreach (Clause rc in resolvents)
{
toAdd.AddAll(rc.getFactors());
}
if (null != tracer)
{
tracer.stepResolved(cI, cJ, toAdd);
}
ansHandler.checkForPossibleAnswers(toAdd);
if (ansHandler.isComplete())
{
break;
}
newClauses.AddAll(toAdd);
}
if (ansHandler.isComplete())
{
break;
}
}
if (ansHandler.isComplete())
{
break;
}
}
noOfPrevClauses = clauses.Size();
// clauses <- clauses <UNION> new
clauses.AddAll(newClauses);
if (ansHandler.isComplete())
{
break;
}
// if new is a <SUBSET> of clauses then finished
// searching for an answer
// (i.e. when they were added the # clauses
// did not increase).
} while (noOfPrevClauses < clauses.Size());
if (null != tracer)
{
tracer.stepFinished(clauses, ansHandler);
}
return(ansHandler);
}
public void testBinaryResolventsOrderDoesNotMatter()
{
// This is a regression test, to ensure
// the ordering of resolvents does not matter.
// If the order ends up mattering, then likely
// a problem was introduced in the Clause class
// unifier, or related class.
// Set up the initial set of clauses based on the
// loves animal domain as it contains functions
// new clauses will always be created (i.e. is an
// infinite universe of discourse).
FOLKnowledgeBase kb = new FOLKnowledgeBase(DomainFactory.lovesAnimalDomain());
kb.tell("FORALL x (FORALL y (Animal(y) => Loves(x, y)) => EXISTS y Loves(y, x))");
kb.tell("FORALL x (EXISTS y (Animal(y) AND Kills(x, y)) => FORALL z NOT(Loves(z, x)))");
kb.tell("FORALL x (Animal(x) => Loves(Jack, x))");
kb.tell("(Kills(Jack, Tuna) OR Kills(Curiosity, Tuna))");
kb.tell("Cat(Tuna)");
kb.tell("FORALL x (Cat(x) => Animal(x))");
ISet <Clause> clauses = CollectionFactory.CreateSet <Clause>();
clauses.AddAll(kb.getAllClauses());
ISet <Clause> newClauses = CollectionFactory.CreateSet <Clause>();
long maxRunTime = 30 * 1000; // 30 seconds
IDateTime finishTime = CommonFactory.Now().AddMilliseconds(maxRunTime);
do
{
clauses.AddAll(newClauses);
newClauses.Clear();
Clause[] clausesA = clauses.ToArray();
for (int i = 0; i < clausesA.Length; ++i)
{
Clause cI = clausesA[i];
for (int j = 0; j < clausesA.Length; j++)
{
Clause cJ = clausesA[j];
newClauses.AddAll(cI.getFactors());
newClauses.AddAll(cJ.getFactors());
ISet <Clause> cIresolvents = cI.binaryResolvents(cJ);
ISet <Clause> cJresolvents = cJ.binaryResolvents(cI);
if (!cIresolvents.SequenceEqual(cJresolvents))
{
System.Console.WriteLine("cI=" + cI);
System.Console.WriteLine("cJ=" + cJ);
System.Console.WriteLine("cIR=" + cIresolvents);
System.Console.WriteLine("cJR=" + cJresolvents);
Assert.Fail("Ordering of binary resolvents has become important, which should not be the case");
}
foreach (Clause r in cIresolvents)
{
newClauses.AddAll(r.getFactors());
}
if (CommonFactory.Now().BiggerThan(finishTime))
{
break;
}
}
if (CommonFactory.Now().BiggerThan(finishTime))
{
break;
}
}
} while (CommonFactory.Now().SmallerThan(finishTime));
}
