I have a simple ontology and trying to do SWRL inference. On Protege 3.5 (build 663) the Jess and Drools engines work as expected while using the SWRL API an error occurs. As described in SWRLRuleEngineAPI I am using the following code:
SWRLRuleEngine ruleEngine = P3SWRLRuleEngineFactory.create(owlModel);
SWRLFactory factory = new SWRLFactory(owlModel);
SWRLImp imp = factory.createImp("Person(?x) ∧ hasGender(?x, male) → Male(?x)");
ruleEngine.infer();
classes = owlModel.getUserDefinedOWLNamedClasses();
for (Iterator it = classes.iterator(); it.hasNext();) {
OWLNamedClass cls = (OWLNamedClass) it.next();
Collection instances = cls.getInstances(false);
System.out.println("Class " + cls.getBrowserText() + " (" + instances.size() + ")");
for (Iterator jt = instances.iterator(); jt.hasNext();) {
OWLIndividual individual = (OWLIndividual) jt.next();
System.out.println(" - " + individual.getBrowserText());
}
}
All Protege API jars are referenced correctly, the code compiles well and the model is read correctly. But the following error appears on both Eclipse and NetBeans when activating the rule engine (SWRLRuleEngine ruleEngine = P3SWRLRuleEngineFactory.create(owlModel)):
INFO: Updating underlying frames model in 1 ms Rule engine 'Jess' registered with the SWRLTab rule engine manager. Oct 14, 2015 8:00:10 AM org.protege.swrltab.p3.P3SWRLRuleEngineFactory registerRuleEngine INFO: Rule engine 'Jess' registered with the SWRLTab rule engine manager. Plugin 'SWRLJessTab' registered with the SWRLTab plugin manager. Oct 14, 2015 8:00:10 AM edu.stanford.smi.protegex.owl.swrl.P3SWRLTabPluginManager registerPlugin INFO: Plugin 'SWRLJessTab' registered with the SWRLTab plugin manager. Rule engine 'Drools' registered with the SWRLTab rule engine manager. Oct 14, 2015 8:00:10 AM org.protege.swrltab.p3.P3SWRLRuleEngineFactory registerRuleEngine INFO: Rule engine 'Drools' registered with the SWRLTab rule engine manager. Plugin 'SWRLDroolsTab' registered with the SWRLTab plugin manager. Oct 14, 2015 8:00:10 AM edu.stanford.smi.protegex.owl.swrl.P3SWRLTabPluginManager registerPlugin INFO: Plugin 'SWRLDroolsTab' registered with the SWRLTab plugin manager. Plugin 'SQWRLQueryTab' registered with the SWRLTab plugin manager. Oct 14, 2015 8:00:10 AM edu.stanford.smi.protegex.owl.swrl.P3SWRLTabPluginManager registerPlugin INFO: Plugin 'SQWRLQueryTab' registered with the SWRLTab plugin manager. java.lang.RuntimeException: wrong class format at org.drools.commons.jci.compilers.EclipseJavaCompiler$2.findType(EclipseJavaCompiler.java:251) at org.drools.commons.jci.compilers.EclipseJavaCompiler$2.findType(EclipseJavaCompiler.java:202) at org.eclipse.jdt.internal.compiler.lookup.LookupEnvironment.askForType(LookupEnvironment.java:109) at org.eclipse.jdt.internal.compiler.lookup.UnresolvedReferenceBinding.resolve(UnresolvedReferenceBinding.java:49) at org.eclipse.jdt.internal.compiler.lookup.BinaryTypeBinding.resolveType(BinaryTypeBinding.java:122) at org.eclipse.jdt.internal.compiler.lookup.BinaryTypeBinding.superInterfaces(BinaryTypeBinding.java:1152) at org.eclipse.jdt.internal.compiler.lookup.ReferenceBinding.implementsInterface(ReferenceBinding.java:888) at org.eclipse.jdt.internal.compiler.lookup.ReferenceBinding.isCompatibleWith0(ReferenceBinding.java:1036) at org.eclipse.jdt.internal.compiler.lookup.ReferenceBinding.isCompatibleWith(ReferenceBinding.java:987) at org.eclipse.jdt.internal.compiler.lookup.Scope.parameterCompatibilityLevel(Scope.java:3963) at org.eclipse.jdt.internal.compiler.lookup.Scope.parameterCompatibilityLevel(Scope.java:3951) at org.eclipse.jdt.internal.compiler.lookup.Scope.computeCompatibleMethod(Scope.java:555) at org.eclipse.jdt.internal.compiler.lookup.Scope.getConstructor(Scope.java:1882) at org.eclipse.jdt.internal.compiler.ast.AllocationExpression.resolveType(AllocationExpression.java:359) at org.eclipse.jdt.internal.compiler.ast.LocalDeclaration.resolve(LocalDeclaration.java:210) at org.eclipse.jdt.internal.compiler.ast.AbstractMethodDeclaration.resolveStatements(AbstractMethodDeclaration.java:463) at org.eclipse.jdt.internal.compiler.ast.MethodDeclaration.resolveStatements(MethodDeclaration.java:252) at org.eclipse.jdt.internal.compiler.ast.AbstractMethodDeclaration.resolve(AbstractMethodDeclaration.java:422) at org.eclipse.jdt.internal.compiler.ast.TypeDeclaration.resolve(TypeDeclaration.java:1148) at org.eclipse.jdt.internal.compiler.ast.TypeDeclaration.resolve(TypeDeclaration.java:1258) at org.eclipse.jdt.internal.compiler.ast.CompilationUnitDeclaration.resolve(CompilationUnitDeclaration.java:538) at org.eclipse.jdt.internal.compiler.Compiler.process(Compiler.java:763) at org.eclipse.jdt.internal.compiler.Compiler.compile(Compiler.java:468) at org.drools.commons.jci.compilers.EclipseJavaCompiler.compile(EclipseJavaCompiler.java:358) at org.drools.commons.jci.compilers.AbstractJavaCompiler.compile(AbstractJavaCompiler.java:49) at org.drools.rule.builder.dialect.java.JavaDialect.compileAll(JavaDialect.java:370) at org.drools.compiler.DialectCompiletimeRegistry.compileAll(DialectCompiletimeRegistry.java:47) at org.drools.compiler.PackageRegistry.compileAll(PackageRegistry.java:101) at org.drools.compiler.PackageBuilder.compileAll(PackageBuilder.java:966) at org.drools.compiler.PackageBuilder.compileAllRules(PackageBuilder.java:802) at org.drools.compiler.PackageBuilder.addPackage(PackageBuilder.java:791) at org.drools.compiler.PackageBuilder.addPackageFromDrl(PackageBuilder.java:462) at org.drools.compiler.PackageBuilder.addKnowledgeResource(PackageBuilder.java:664) at org.drools.builder.impl.KnowledgeBuilderImpl.add(KnowledgeBuilderImpl.java:48) at org.drools.builder.impl.KnowledgeBuilderImpl.add(KnowledgeBuilderImpl.java:35) at org.protege.swrlapi.drools.DroolsSWRLRuleEngine.defineDRLResource(Unknown Source) at org.protege.swrlapi.drools.DroolsSWRLRuleEngine.defineDRLRule(Unknown Source) at org.protege.swrlapi.drools.DroolsSWRLRuleEngine.resetRuleEngine(Unknown Source) at org.protege.swrlapi.drools.DroolsSWRLRuleEngine.(Unknown Source) at org.protege.swrlapi.drools.DroolsSWRLRuleEngineCreator.create(Unknown Source) at org.protege.swrltab.p3.P3SWRLRuleEngineFactory.create(Unknown Source) at org.protege.swrltab.p3.P3SWRLRuleEngineFactory.create(Unknown Source) at com.demo.application.OWLAPIDemoApplication.main(OWLAPIDemoApplication.java:107) Caused by: org.eclipse.jdt.internal.compiler.classfmt.ClassFormatException at org.eclipse.jdt.internal.compiler.classfmt.ClassFileReader.(ClassFileReader.java:372) at org.drools.commons.jci.compilers.EclipseJavaCompiler$2.createNameEnvironmentAnswer(EclipseJavaCompiler.java:275) at org.drools.commons.jci.compilers.EclipseJavaCompiler$2.findType(EclipseJavaCompiler.java:246) ... 42 more Exception in thread "main" org.protege.swrlapi.exceptions.SWRLRuleEngineException: Error creating rule engine Drools. Exception: org.protege.owl.portability.exceptions.TargetRuleEngineException. Message: internal error generating Drools rule rule scm_cls when CDA($c:c) then SCA sca1=new SCA($c, $c); ECA eca=new ECA($c, $c); SCA sca2=new SCA($c, "owl:Thing"); SCA sca3=new SCA("owl:Nothing", $c); inferrer.infer(sca1, eca, sca2, sca3); end wrong class format at org.protege.swrltab.p3.P3SWRLRuleEngineFactory.create(Unknown Source) at org.protege.swrltab.p3.P3SWRLRuleEngineFactory.create(Unknown Source) at com.demo.application.OWLAPIDemoApplication.main(OWLAPIDemoApplication.java:107) Caused by: org.protege.owl.portability.exceptions.TargetRuleEngineException: internal error generating Drools rule rule scm_cls when CDA($c:c) then SCA sca1=new SCA($c, $c); ECA eca=new ECA($c, $c); SCA sca2=new SCA($c, "owl:Thing"); SCA sca3=new SCA("owl:Nothing", $c); inferrer.infer(sca1, eca, sca2, sca3); end wrong class format at org.protege.swrlapi.drools.DroolsSWRLRuleEngine.defineDRLRule(Unknown Source) at org.protege.swrlapi.drools.DroolsSWRLRuleEngine.resetRuleEngine(Unknown Source) at org.protege.swrlapi.drools.DroolsSWRLRuleEngine.(Unknown Source) at org.protege.swrlapi.drools.DroolsSWRLRuleEngineCreator.create(Unknown Source) ... 3 more Caused by: java.lang.RuntimeException: wrong class format at org.drools.commons.jci.compilers.EclipseJavaCompiler$2.findType(EclipseJavaCompiler.java:251) at org.drools.commons.jci.compilers.EclipseJavaCompiler$2.findType(EclipseJavaCompiler.java:202) at org.eclipse.jdt.internal.compiler.lookup.LookupEnvironment.askForType(LookupEnvironment.java:109) at org.eclipse.jdt.internal.compiler.lookup.UnresolvedReferenceBinding.resolve(UnresolvedReferenceBinding.java:49) at org.eclipse.jdt.internal.compiler.lookup.BinaryTypeBinding.resolveType(BinaryTypeBinding.java:122) at org.eclipse.jdt.internal.compiler.lookup.BinaryTypeBinding.superInterfaces(BinaryTypeBinding.java:1152) at org.eclipse.jdt.internal.compiler.lookup.ReferenceBinding.implementsInterface(ReferenceBinding.java:888) at org.eclipse.jdt.internal.compiler.lookup.ReferenceBinding.isCompatibleWith0(ReferenceBinding.java:1036) at org.eclipse.jdt.internal.compiler.lookup.ReferenceBinding.isCompatibleWith(ReferenceBinding.java:987) at org.eclipse.jdt.internal.compiler.lookup.Scope.parameterCompatibilityLevel(Scope.java:3963) at org.eclipse.jdt.internal.compiler.lookup.Scope.parameterCompatibilityLevel(Scope.java:3951) at org.eclipse.jdt.internal.compiler.lookup.Scope.computeCompatibleMethod(Scope.java:555) at org.eclipse.jdt.internal.compiler.lookup.Scope.getConstructor(Scope.java:1882) at org.eclipse.jdt.internal.compiler.ast.AllocationExpression.resolveType(AllocationExpression.java:359) at org.eclipse.jdt.internal.compiler.ast.LocalDeclaration.resolve(LocalDeclaration.java:210) at org.eclipse.jdt.internal.compiler.ast.AbstractMethodDeclaration.resolveStatements(AbstractMethodDeclaration.java:463) at org.eclipse.jdt.internal.compiler.ast.MethodDeclaration.resolveStatements(MethodDeclaration.java:252) at org.eclipse.jdt.internal.compiler.ast.AbstractMethodDeclaration.resolve(AbstractMethodDeclaration.java:422) at org.eclipse.jdt.internal.compiler.ast.TypeDeclaration.resolve(TypeDeclaration.java:1148) at org.eclipse.jdt.internal.compiler.ast.TypeDeclaration.resolve(TypeDeclaration.java:1258) at org.eclipse.jdt.internal.compiler.ast.CompilationUnitDeclaration.resolve(CompilationUnitDeclaration.java:538) at org.eclipse.jdt.internal.compiler.Compiler.process(Compiler.java:763) at org.eclipse.jdt.internal.compiler.Compiler.compile(Compiler.java:468) at org.drools.commons.jci.compilers.EclipseJavaCompiler.compile(EclipseJavaCompiler.java:358) at org.drools.commons.jci.compilers.AbstractJavaCompiler.compile(AbstractJavaCompiler.java:49) at org.drools.rule.builder.dialect.java.JavaDialect.compileAll(JavaDialect.java:370) at org.drools.compiler.DialectCompiletimeRegistry.compileAll(DialectCompiletimeRegistry.java:47) at org.drools.compiler.PackageRegistry.compileAll(PackageRegistry.java:101) at org.drools.compiler.PackageBuilder.compileAll(PackageBuilder.java:966) at org.drools.compiler.PackageBuilder.compileAllRules(PackageBuilder.java:802) at org.drools.compiler.PackageBuilder.addPackage(PackageBuilder.java:791) at org.drools.compiler.PackageBuilder.addPackageFromDrl(PackageBuilder.java:462) at org.drools.compiler.PackageBuilder.addKnowledgeResource(PackageBuilder.java:664) at org.drools.builder.impl.KnowledgeBuilderImpl.add(KnowledgeBuilderImpl.java:48) at org.drools.builder.impl.KnowledgeBuilderImpl.add(KnowledgeBuilderImpl.java:35) at org.protege.swrlapi.drools.DroolsSWRLRuleEngine.defineDRLResource(Unknown Source) ... 7 more Caused by: org.eclipse.jdt.internal.compiler.classfmt.ClassFormatException at org.eclipse.jdt.internal.compiler.classfmt.ClassFileReader.(ClassFileReader.java:372) at org.drools.commons.jci.compilers.EclipseJavaCompiler$2.createNameEnvironmentAnswer(EclipseJavaCompiler.java:275) at org.drools.commons.jci.compilers.EclipseJavaCompiler$2.findType(EclipseJavaCompiler.java:246) ... 42 more Java Result: 1
UPDATE: After downgrading to Java 7 the following issue appears:
Exception in thread "main" java.lang.NullPointerException at org.protege.owl.portability.p3.converters.P3OWLAxiomConverter.completeBulkConversion(Unknown Source) at org.protege.swrlapi.core.impl.AbstractSWRLRuleEngine.writeInferredKnowledge2OWL(Unknown Source) at org.protege.swrlapi.core.impl.AbstractSWRLRuleEngine.infer(Unknown Source) at com.demo.application.OWLAPIDemoApplication.main(OWLAPIDemoApplication.java:125) Java Result: 1
It was the Protege version issue. I resolved that by downgrading to the 3.4.8 version which was suggested by Martin O'Connor Answer which has been under extensive review. Thank you all for your efforts.