IndexOutOfBoundsException in BetaNode.java for rules with multiple atoms like p(?x,?x), p(?y, ?y)

[Christian-D]

When using multiple atoms with only one variable each in context of an DL-safe rule, the call PelletReasoner.getKB.realize() fails with the following exception:

Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 1, Size: 1
at java.util.ArrayList.rangeCheck(Unknown Source)
at java.util.ArrayList.get(Unknown Source)
at com.clarkparsia.pellet.rules.rete.BetaNode.join(BetaNode.java:123)
at com.clarkparsia.pellet.rules.rete.Interpreter.processBetaNodes(Interpreter.java:109)
at com.clarkparsia.pellet.rules.rete.Interpreter.run(Interpreter.java:236)
at com.clarkparsia.pellet.rules.ContinuousRulesStrategy.applyRete(ContinuousRulesStrategy.java:179)
at com.clarkparsia.pellet.rules.ContinuousRulesStrategy.complete(ContinuousRulesStrategy.java:322)
at org.mindswap.pellet.ABox.isConsistent(ABox.java:1423)
at org.mindswap.pellet.ABox.isConsistent(ABox.java:1260)
at org.mindswap.pellet.KnowledgeBase.consistency(KnowledgeBase.java:1987)
at org.mindswap.pellet.KnowledgeBase.isConsistent(KnowledgeBase.java:2061)
at org.mindswap.pellet.KnowledgeBase.ensureConsistency(KnowledgeBase.java:2075)
at org.mindswap.pellet.KnowledgeBase.classify(KnowledgeBase.java:2083)
at org.mindswap.pellet.KnowledgeBase.realize(KnowledgeBase.java:2111)

The "rolification" of a class is used to increase the performance of the reasoning process. The following model (functional syntax) may be used to reproduce the error:

Prefix(owl:=http://www.w3.org/2002/07/owl#)
Prefix(rdf:=http://www.w3.org/1999/02/22-rdf-syntax-ns#)
Prefix(xml:=http://www.w3.org/XML/1998/namespace)
Prefix(xsd:=http://www.w3.org/2001/XMLSchema#)
Prefix(rdfs:=http://www.w3.org/2000/01/rdf-schema#)

Ontology(http://www.semanticweb.org/ontologies/2014/3/untitled-ontology-215
Import(http://www.w3.org/2006/time)

EquivalentClasses(http://www.w3.org/2006/time#Instant ObjectHasSelf(http://www.semanticweb.org/ontologies/2014/3/untitled-ontology-215#R_Instant))
Declaration(ObjectProperty(http://www.semanticweb.org/ontologies/2014/3/untitled-ontology-215#R_Instant))
Declaration(NamedIndividual(http://www.semanticweb.org/ontologies/2014/3/untitled-ontology-215#Instant1))
ClassAssertion(http://www.w3.org/2006/time#Instant http://www.semanticweb.org/ontologies/2014/3/untitled-ontology-215#Instant1)
DataPropertyAssertion(http://www.w3.org/2006/time#inXSDDateTime http://www.semanticweb.org/ontologies/2014/3/untitled-ontology-215#Instant1 "2000-01-01T00:00:00"^^xsd:dateTime)
Declaration(NamedIndividual(http://www.semanticweb.org/ontologies/2014/3/untitled-ontology-215#Instant2))
ClassAssertion(http://www.w3.org/2006/time#Instant http://www.semanticweb.org/ontologies/2014/3/untitled-ontology-215#Instant2)
DataPropertyAssertion(http://www.w3.org/2006/time#inXSDDateTime http://www.semanticweb.org/ontologies/2014/3/untitled-ontology-215#Instant2 "2003-01-01T00:00:00"^^xsd:dateTime)
DLSafeRule(Body(ObjectPropertyAtom(http://www.semanticweb.org/ontologies/2014/3/untitled-ontology-215#R_Instant Variable(urn:swrl#x) Variable(urn:swrl#x)) ObjectPropertyAtom(http://www.semanticweb.org/ontologies/2014/3/untitled-ontology-215#R_Instant Variable(urn:swrl#z) Variable(urn:swrl#z)) DataPropertyAtom(http://www.w3.org/2006/time#inXSDDateTime Variable(urn:swrl#x) Variable(urn:swrl#y)) DataPropertyAtom(http://www.w3.org/2006/time#inXSDDateTime Variable(urn:swrl#z) Variable(urn:swrl#w)) BuiltInAtom(http://www.w3.org/2003/11/swrlb#lessThan Variable(urn:swrl#y) Variable(urn:swrl#w)))Head(ObjectPropertyAtom(http://www.w3.org/2006/time#before Variable(urn:swrl#x) Variable(urn:swrl#z))))
)

[Christian-D]

I found this related ticket: https://clark-parsia.trac.cvsdude.com/pellet-devel/ticket/382 . The fix (I suppose it is the if-condition at lines 118-119 of the BetaNode class ?) works for one expression like p(?x, ?x), but two or more will fail. Maybe these lines may need to be revised when considering a fix.