//
// 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));
}
public void testFindSubsumedClauses()
{
// Taken from AIMA2e pg 679
FOLDomain domain = new FOLDomain();
domain.addPredicate("patrons");
domain.addPredicate("hungry");
domain.addPredicate("type");
domain.addPredicate("fri_sat");
domain.addPredicate("will_wait");
domain.addConstant("Some");
domain.addConstant("Full");
domain.addConstant("French");
domain.addConstant("Thai");
domain.addConstant("Burger");
FOLParser parser = new FOLParser(domain);
String c1 = "patrons(v,Some)";
String c2 = "patrons(v,Full) AND (hungry(v) AND type(v,French))";
String c3 = "patrons(v,Full) AND (hungry(v) AND (type(v,Thai) AND fri_sat(v)))";
String c4 = "patrons(v,Full) AND (hungry(v) AND type(v,Burger))";
String sh = "FORALL v (will_wait(v) <=> (" + c1 + " OR (" + c2
+ " OR (" + c3 + " OR (" + c4 + ")))))";
Sentence s = parser.parse(sh);
CNFConverter cnfConv = new CNFConverter(parser);
CNF cnf = cnfConv.convertToCNF(s);
// Contains 9 duplicates
Assert.AreEqual(40, cnf.getNumberOfClauses());
List <Clause> clauses = new List <Clause>(cnf.getConjunctionOfClauses());
// duplicates removed
Assert.AreEqual(31, clauses.Count);
foreach (Clause remove in SubsumptionElimination.findSubsumedClauses(clauses))
{
clauses.Remove(remove);
}
// subsumed clauses removed
Assert.AreEqual(8, clauses.Count);
// Ensure only the 8 correct/expected clauses remain
Clause cl1 = cnfConv
.convertToCNF(
parser
.parse("(NOT(will_wait(v)) OR (patrons(v,Full) OR patrons(v,Some)))"))
.getConjunctionOfClauses()[0];
Clause cl2 = cnfConv
.convertToCNF(
parser
.parse("(NOT(will_wait(v)) OR (hungry(v) OR patrons(v,Some)))"))
.getConjunctionOfClauses()[0];
Clause cl3 = cnfConv
.convertToCNF(
parser
.parse("(NOT(will_wait(v)) OR (patrons(v,Some) OR (type(v,Burger) OR (type(v,French) OR type(v,Thai)))))"))
.getConjunctionOfClauses()[0];
Clause cl4 = cnfConv
.convertToCNF(
parser
.parse("(NOT(will_wait(v)) OR (fri_sat(v) OR (patrons(v,Some) OR (type(v,Burger) OR type(v,French)))))"))
.getConjunctionOfClauses()[0];
Clause cl5 = cnfConv.convertToCNF(
parser.parse("(NOT(patrons(v,Some)) OR will_wait(v))"))
.getConjunctionOfClauses()[0];
Clause cl6 = cnfConv
.convertToCNF(
parser
.parse("(NOT(hungry(v)) OR (NOT(patrons(v,Full)) OR (NOT(type(v,French)) OR will_wait(v))))"))
.getConjunctionOfClauses()[0];
Clause cl7 = cnfConv
.convertToCNF(
parser
.parse("(NOT(fri_sat(v)) OR (NOT(hungry(v)) OR (NOT(patrons(v,Full)) OR (NOT(type(v,Thai)) OR will_wait(v)))))"))
.getConjunctionOfClauses()[0];
Clause cl8 = cnfConv
.convertToCNF(
parser
.parse("(NOT(hungry(v)) OR (NOT(patrons(v,Full)) OR (NOT(type(v,Burger)) OR will_wait(v))))"))
.getConjunctionOfClauses()[0];
Assert.IsTrue(clauses.Contains(cl1));
Assert.IsTrue(clauses.Contains(cl2));
Assert.IsTrue(clauses.Contains(cl3));
Assert.IsTrue(clauses.Contains(cl4));
Assert.IsTrue(clauses.Contains(cl5));
Assert.IsTrue(clauses.Contains(cl6));
Assert.IsTrue(clauses.Contains(cl7));
Assert.IsTrue(clauses.Contains(cl8));
}