// END-Sentence
//
public override bool Equals(Object o)
{
if (this == o)
{
return(true);
}
if ((o == null) || !(o is NotSentence))
{
return(false);
}
NotSentence ns = (NotSentence)o;
return(ns.negated.Equals(negated));
}
protected void testFullFOLKBLovesAnimalQueryNotKillsJackTunaSucceeds(
InferenceProcedure infp, bool expectedToTimeOut)
{
FOLKnowledgeBase akb = FOLKnowledgeBaseFactory
.createLovesAnimalKnowledgeBase(infp);
List<Term> terms = new List<Term>();
terms.Add(new Constant("Jack"));
terms.Add(new Constant("Tuna"));
NotSentence query = new NotSentence(new Predicate("Kills", terms));
InferenceResult answer = akb.ask(query);
Assert.IsTrue(null != answer);
if (expectedToTimeOut)
{
Assert.IsFalse(answer.isPossiblyFalse());
Assert.IsFalse(answer.isTrue());
Assert.IsTrue(answer.isUnknownDueToTimeout());
Assert.IsFalse(answer.isPartialResultDueToTimeout());
Assert.IsTrue(0 == answer.getProofs().Count);
}
else
{
Assert.IsFalse(answer.isPossiblyFalse());
Assert.IsTrue(answer.isTrue());
Assert.IsFalse(answer.isUnknownDueToTimeout());
Assert.IsFalse(answer.isPartialResultDueToTimeout());
Assert.IsTrue(1 == answer.getProofs().Count);
Assert.IsTrue(0 == answer.getProofs()[0]
.getAnswerBindings().Count);
}
}
//
// PRIVATE METHODS
//
private void constructFOLEg() {
ithExampleConstant = new Constant(folDSDomain.getExampleConstant(egNo));
List<Term> terms = new List<Term>();
terms.Add(ithExampleConstant);
// Create the classification sentence
classification = new Predicate(folDSDomain.getGoalPredicateName(),
terms);
if (!example.getAttributeValueAsString(
folDSDomain.getDataSetTargetName()).Equals(
folDSDomain.getTrueGoalValue())) {
// if not true then needs to be a Not sentence
classification = new NotSentence(classification);
}
// Create the description sentence
List<Sentence> descParts = new List<Sentence>();
foreach (String dname in folDSDomain.getDescriptionDataSetNames()) {
String foldDName = folDSDomain.getFOLName(dname);
terms = new List<Term>();
terms.Add(ithExampleConstant);
// If multivalued becomes a two place predicate
// e.g: Patrons(X1, Some)
// otherwise: Hungry(X1) or ~ Hungry(X1)
// see pg 769 of AIMA
Sentence part = null;
if (folDSDomain.isMultivalued(dname)) {
terms.Add(new Constant(folDSDomain.getFOLName(example
.getAttributeValueAsString(dname))));
part = new Predicate(foldDName, terms);
} else {
part = new Predicate(foldDName, terms);
// Need to determine if false
if (!folDSDomain.getTrueGoalValue().Equals(
example.getAttributeValueAsString(dname))) {
part = new NotSentence(part);
}
}
descParts.Add(part);
}
if (descParts.Count == 1) {
description = descParts[0];
} else if (descParts.Count > 1) {
description = new ConnectedSentence(Connectors.AND, descParts
[0], descParts[1]);
for (int i = 2; i < descParts.Count; i++) {
description = new ConnectedSentence(Connectors.AND,
description, descParts[i]);
}
}
}
public Object visitNotSentence(NotSentence sentence, Object arg)
{
sentence.getNegated().accept(this, arg);
return arg;
}
public Object visitNotSentence(NotSentence sentence, Object arg)
{
ArgData ad = (ArgData)arg;
// Indicate that the enclosed predicate is negated
ad.negated = true;
sentence.getNegated().accept(this, arg);
ad.negated = false;
return sentence;
}
public Object visitNotSentence(NotSentence sentence, Object arg)
{
return new NotSentence((Sentence)sentence.getNegated().accept(this,
arg));
}
public Object visitNotSentence(NotSentence notSentence, Object arg)
{
// CNF requires NOT (~) to appear only in literals, so we 'move ~
// inwards' by repeated application of the following equivalences:
Sentence negated = notSentence.getNegated();
// ~(~alpha) equivalent to alpha (double negation elimination)
if (negated is NotSentence)
{
return ((NotSentence)negated).getNegated().accept(this, arg);
}
if (negated is ConnectedSentence)
{
ConnectedSentence negConnected = (ConnectedSentence)negated;
Sentence alpha = negConnected.getFirst();
Sentence beta = negConnected.getSecond();
// ~(alpha ^ beta) equivalent to (~alpha V ~beta) (De Morgan)
if (Connectors.isAND(negConnected.getConnector()))
{
// I need to ensure the ~s are moved in deeper
Sentence notAlpha = (Sentence)(new NotSentence(alpha)).accept(
this, arg);
Sentence notBeta = (Sentence)(new NotSentence(beta)).accept(
this, arg);
return new ConnectedSentence(Connectors.OR, notAlpha, notBeta);
}
// ~(alpha V beta) equivalent to (~alpha ^ ~beta) (De Morgan)
if (Connectors.isOR(negConnected.getConnector()))
{
// I need to ensure the ~s are moved in deeper
Sentence notAlpha = (Sentence)(new NotSentence(alpha)).accept(
this, arg);
Sentence notBeta = (Sentence)(new NotSentence(beta)).accept(
this, arg);
return new ConnectedSentence(Connectors.AND, notAlpha, notBeta);
}
}
// in addition, rules for negated quantifiers:
if (negated is QuantifiedSentence)
{
QuantifiedSentence negQuantified = (QuantifiedSentence)negated;
// I need to ensure the ~ is moved in deeper
Sentence notP = (Sentence)(new NotSentence(negQuantified
.getQuantified())).accept(this, arg);
// ~FORALL x p becomes EXISTS x ~p
if (Quantifiers.isFORALL(negQuantified.getQuantifier()))
{
return new QuantifiedSentence(Quantifiers.EXISTS, negQuantified
.getVariables(), notP);
}
// ~EXISTS x p becomes FORALL x ~p
if (Quantifiers.isEXISTS(negQuantified.getQuantifier()))
{
return new QuantifiedSentence(Quantifiers.FORALL, negQuantified
.getVariables(), notP);
}
}
return new NotSentence((Sentence)negated.accept(this, arg));
}
public Object visitNotSentence(NotSentence notSentence, Object arg)
{
Sentence negated = notSentence.getNegated();
return new NotSentence((Sentence)negated.accept(this, arg));
}
public AnswerHandler(FOLKnowledgeBase kb, Sentence aQuery,
long maxQueryTime, FOLModelElimination folModelElimination)
{
finishTime = System.DateTime.UtcNow.Ticks + maxQueryTime;
Sentence refutationQuery = new NotSentence(aQuery);
// Want to use an answer literal to pull
// query variables where necessary
Literal answerLiteral = kb.createAnswerLiteral(refutationQuery);
answerLiteralVariables = kb.collectAllVariables(answerLiteral
.getAtomicSentence());
// Create the Set of Support based on the Query.
if (answerLiteralVariables.Count > 0)
{
Sentence refutationQueryWithAnswer = new ConnectedSentence(
Connectors.OR, refutationQuery, (Sentence)answerLiteral
.getAtomicSentence().copy());
sos = folModelElimination.createChainsFromClauses(kb
.convertToClauses(refutationQueryWithAnswer));
answerChain.addLiteral(answerLiteral);
}
else
{
sos = folModelElimination.createChainsFromClauses(kb
.convertToClauses(refutationQuery));
}
foreach (Chain s in sos)
{
s.setProofStep(new ProofStepGoal(s));
}
}
//
// 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
/**
* <code>
* function FOL-FC-ASK(KB, alpha) returns a substitution or false
* inputs: KB, the knowledge base, a set of first order definite clauses
* alpha, the query, an atomic sentence
* </code>
*/
public InferenceResult ask(FOLKnowledgeBase KB, Sentence query)
{
// Assertions on the type of queries this Inference procedure
// supports
if (!(query is AtomicSentence))
{
throw new ArgumentException(
"Only Atomic Queries are supported.");
}
FCAskAnswerHandler ansHandler = new FCAskAnswerHandler();
Literal alpha = new Literal((AtomicSentence)query);
// local variables: new, the new sentences inferred on each iteration
List<Literal> newSentences = new List<Literal>();
// Ensure query is not already a know fact before
// attempting forward chaining.
List<Dictionary<Variable, Term>> answers = KB.fetch(alpha);
if (answers.Count > 0)
{
ansHandler.addProofStep(new ProofStepFoChAlreadyAFact(alpha));
ansHandler.setAnswers(answers);
return ansHandler;
}
// repeat until new is empty
do
{
// new <- {}
newSentences.Clear();
// for each rule in KB do
// (p1 ^ ... ^ pn => q) <-STANDARDIZE-VARIABLES(rule)
foreach (Clause impl in KB.getAllDefiniteClauseImplications())
{
Clause impl2 = KB.standardizeApart(impl);
// for each theta such that SUBST(theta, p1 ^ ... ^ pn) =
// SUBST(theta, p'1 ^ ... ^ p'n)
// --- for some p'1,...,p'n in KB
foreach (Dictionary<Variable, Term> theta in KB.fetch(invert(new List<Literal>(impl2
.getNegativeLiterals()))))
{
// q' <- SUBST(theta, q)
Literal qPrime = KB.subst(theta, impl.getPositiveLiterals()
[0]);
// if q' does not unify with some sentence already in KB or
// new then do
if (!KB.isRenaming(qPrime)
&& !KB.isRenaming(qPrime, newSentences))
{
// add q' to new
newSentences.Add(qPrime);
ansHandler.addProofStep(impl, qPrime, theta);
// theta <- UNIFY(q', alpha)
Dictionary<Variable, Term> theta2 = KB.unify(qPrime.getAtomicSentence(), alpha
.getAtomicSentence());
// if theta is not fail then return theta
if (null != theta2)
{
foreach (Literal l in newSentences)
{
Sentence s = null;
if (l.isPositiveLiteral())
{
s = l.getAtomicSentence();
}
else
{
s = new NotSentence(l.getAtomicSentence());
}
KB.tell(s);
}
ansHandler.setAnswers(KB.fetch(alpha));
return ansHandler;
}
}
}
}
// add new to KB
foreach (Literal l in newSentences)
{
Sentence s = null;
if (l.isPositiveLiteral())
{
s = l.getAtomicSentence();
}
else
{
s = new NotSentence(l.getAtomicSentence());
}
KB.tell(s);
}
} while (newSentences.Count > 0);
// return false
return ansHandler;
}
public Object visitNotSentence(NotSentence sentence, Object arg)
{
throw new NotImplementedException(
"visitNotSentence() should not be called.");
}
//
// START-InferenceProcedure
public InferenceResult ask(FOLKnowledgeBase KB, Sentence alpha)
{
// clauses <- the set of clauses in CNF representation of KB ^ ~alpha
List<Clause> clauses = new List<Clause>();
foreach (Clause c in KB.getAllClauses())
{
Clause c2 = KB.standardizeApart(c);
c2.setStandardizedApartCheckNotRequired();
clauses.AddRange(c2.getFactors());
}
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();
clauses.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();
clauses.AddRange(c2.getFactors());
}
}
TFMAnswerHandler ansHandler = new TFMAnswerHandler(answerLiteral,
answerLiteralVariables, answerClause, maxQueryTime);
// new <- {}
List<Clause> newClauses = new List<Clause>();
List<Clause> toAdd = new List<Clause>();
// loop do
int noOfPrevClauses = clauses.Count;
do
{
if (null != tracer)
{
tracer.stepStartWhile(clauses, clauses.Count, newClauses
.Count);
}
newClauses.Clear();
// for each Ci, Cj in clauses do
Clause[] clausesA = new Clause[clauses.Count];
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)
List<Clause> resolvents = cI.binaryResolvents(cJ);
if (resolvents.Count > 0)
{
toAdd.Clear();
// new <- new <UNION> resolvent
foreach (Clause rc in resolvents)
{
toAdd.AddRange(rc.getFactors());
}
if (null != tracer)
{
tracer.stepResolved(cI, cJ, toAdd);
}
ansHandler.checkForPossibleAnswers(toAdd);
if (ansHandler.isComplete())
{
break;
}
newClauses.AddRange(toAdd);
}
if (ansHandler.isComplete())
{
break;
}
}
if (ansHandler.isComplete())
{
break;
}
}
noOfPrevClauses = clauses.Count;
// clauses <- clauses <UNION> new
clauses.AddRange(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.Count);
if (null != tracer)
{
tracer.stepFinished(clauses, ansHandler);
}
return ansHandler;
}
