NullPointerException when Precomputing Inferences

[tobiaswjohn]

I am using Openllet to compute the class hierarchy of an ontology. I discovered a case, where Openllet throws an exception.

• The input ontology for which the exception occurs is too large to add it in the text here, but can be found in the following github repository
• Here is the call from my program:

OWLOntologyDocumentSource source = new FileDocumentSource(ontFile, new FunctionalSyntaxDocumentFormat());
OWLOntologyManager manager = OWLManager.createOWLOntologyManager();
OwlOntology ont = manager.loadOntologyFromOntologyDocument(source);

OpenlletReasonerFactory rf = new OpenlletReasonerFactory();
OWLReasoner openllet = rf.createReasoner(ont);

/// precomputation for class hierarchy
if (openllet.isConsistent()) {
 openllet.precomputeInferences(InferenceType.CLASS_HIERARCHY);
}

• the following exception is thrown:

Exception in thread "main" java.lang.NullPointerException: Cannot invoke "openllet.core.boxes.abox.Individual.isMerged()" because "node1" is null
	at openllet.core.rules.RuleAtomAsserter.addEdge(RuleAtomAsserter.java:107)
	at openllet.core.rules.RuleAtomAsserter.visit(RuleAtomAsserter.java:163)
	at openllet.core.rules.model.IndividualPropertyAtom.accept(IndividualPropertyAtom.java:35)
	at openllet.core.rules.RuleAtomAsserter.assertAtom(RuleAtomAsserter.java:68)
	at openllet.core.tableau.branch.RuleBranch.tryBranch(RuleBranch.java:139)
	at openllet.core.tableau.branch.Branch.tryNext(Branch.java:130)
	at openllet.core.rules.ContinuousRulesStrategy.createDisjunctionsFromBinding(ContinuousRulesStrategy.java:363)
	at openllet.core.rules.ContinuousRulesStrategy.applyRuleBindings(ContinuousRulesStrategy.java:171)
	at openllet.core.rules.ContinuousRulesStrategy.complete(ContinuousRulesStrategy.java:262)
	at openllet.core.boxes.abox.ABoxImpl.lambda$isConsistent$12(ABoxImpl.java:1417)
	at openllet.core.utils.Timers.execute(Timers.java:118)
	at openllet.core.boxes.abox.ABoxImpl.isConsistent(ABoxImpl.java:1417)
	at openllet.core.boxes.abox.ABoxImpl.existType(ABoxImpl.java:905)
	at openllet.core.knowledge.InstancesBase.retrieve(InstancesBase.java:268)
	at openllet.core.KnowledgeBaseImplFullSync.retrieve(KnowledgeBaseImplFullSync.java:733)
	at openllet.core.taxonomy.CDOptimizedTaxonomyBuilder.realizeByConcept(CDOptimizedTaxonomyBuilder.java:1353)
	at openllet.core.taxonomy.CDOptimizedTaxonomyBuilder.realizeByConcept(CDOptimizedTaxonomyBuilder.java:1361)
	at openllet.core.taxonomy.CDOptimizedTaxonomyBuilder.realizeByConcepts(CDOptimizedTaxonomyBuilder.java:1322)
	at openllet.core.taxonomy.CDOptimizedTaxonomyBuilder.realize(CDOptimizedTaxonomyBuilder.java:1181)
	at openllet.core.KnowledgeBaseImpl.realize(KnowledgeBaseImpl.java:1950)
	at openllet.core.KnowledgeBaseImplFullSync.realize(KnowledgeBaseImplFullSync.java:391)
	at openllet.owlapi.PelletReasoner.precomputeInferences(PelletReasoner.java:1292)