1 OWL Instance Data Evaluation Li Ding, Jiao Tao, and Deborah L. McGuinness Tetherless World Constellation Computer Science Department

2 Motivation Focus of this talk –OWL instance data Why is it interesting? –Instance data dwarfs class data on the web –Instance data may be published independently from class and property descriptions and may cause unexpected issues –Instance data is often used by many applications, some of which may not be aware of the class and property descriptions

3 A new ontologyA new instance data Wine ontology Semantic Inconsistency in Distributed Publishing wine:EarlyHarvest wine:LateHarvest wine:Wine rdfs:subClassOf owl:disjointWith wine:BadWineDefinition rdfs:subClassOf wi:BadWineInstance rdf:type Case1: semantic inconsistency caused by a new class. Case2: semantic inconsistency caused by a new instance.

4 Limited Scope of Data Instance data A Instance Data B Wine ontology wine:Zinfandel wine:Wine rdfs:subClassOf wi:W1 rdf:type Consider Instance data A, application may need additional instance data to meet cardinality requirement Surfing via namespace of wine ontology wine:hasMaker owl:Restriction "1"^xsd:nonNegativeInteger rdfs:subClassOf owl:onProperty owl:cardinality wi:WineMaker1 wine:hasMaker wine:Red wine:hasColor

5 Issues with OWL instance data General Issues –RDF syntax –OWL DL semantic consistency Issues related to an individual’s type description: –Unexpected individual type: (rdfs:domain, rdfs:range, owl:allValuesFrom) –Redundant individual type –Non-specific individual type Issues related to property restrictions: –Unexpected individual type: (owl:hasValue) –Missing property value (owl:minCardinality, owl:cardinality) –Excessive property value (owl:maxCardinality, owl:cardinality) (Customizable and Extensible) Issues related to style: –Naming conventions –Missing annotations,…

6 Implementation Load instance data - (D) –Is D syntactically correct? Load the corresponding ontologies - (O={O1,O2,…}) –Is any Oi inaccessible? Derive the inferred model, - Inf(D+O) –Is D semantically consistent with O? Use Pellet OWL DL reasoner Check style issues –Is more explicit description about the instance needed? Run Sparql on (D) and Inf( D+O ) –query D to confirm the issue is caused by D –query Inf(D+O) to check presence of issue –Is there any redundancy or ambiguity in D?

7 Wine Ontology (Partial) Class(a:Wine partial restriction(a:hasSugar cardinality(1)) restriction(a:madeFromGrape minCardinality(1)) restriction(a:hasBody cardinality(1)) restriction(a:hasColor cardinality(1)) restriction(a:hasFlavor cardinality(1)) restriction(a:hasMaker cardinality(1)) restriction(a:locatedIn someValuesFrom(a:Region)) restriction(a:hasMaker allValuesFrom(a:Winery))) Class(a:Zinfandel complete intersectionOf( restriction(a:madeFromGrape value (a:ZinfandelGrape)) a:Wine restriction(a:madeFromGrape maxCardinality(1)))) Class(a:Zinfandel partial restriction(a:hasSugar value (a:Dry)) restriction(a:hasFlavor allValuesFrom(oneOf(a:Moderate a:Strong))) restriction(a:hasBody allValuesFrom(oneOf(a:Medium a:Full))) restriction(a:hasColor value (a:Red)))

8 An Example SPARQL Query for Missing Property Value 1.PREFIX rdf: 2.PREFIX rdfs: 3.PREFIX owl: 4.SELECT ?i ?p ?c 5.FROM NAMED 6.WHERE { { ?c rdfs:subClassOf ?r. 7. ?r rdf:type owl:Restriction. 8. ?r owl:onProperty ?p. 9. ?r owl:cardinality ?card. 10. FILTER( ?card = 1 ) 11. OPTIONAL { ?i ?p ?o. } 12. "FILTER( !BOUND(?o) ) } 13. GRAPH 14. { ?i rdf:type ?c. } }

9 Conclusion Current work –identified OWL instance data evaluation problem –Listed several common issues in OWL instance data –used SPARQL + Inference to clarify issue definition and simplify issue detection Future work –Use SPARQL-DL API

10 Questions? or More Slides? The 7th International Semantic Web Conference ISWC 2008 Karlsruhe DE October

11 A Questionnaire for OWL User Experiences OWL constructs –What have been used? –What are still missing? OWL inference –What inference has been used to solve problem? –What other inference is used together with OWL inference, e.g. sparql, swrl? OWL user experience –How hard is it to build/reuse OWL ontology –How hard is it to build/reuse OWL instance data –How OWL help web users?

12 OWL Instance Data Evaluation Architecture semantic web data evaluation services RDF parsing and validation referenced ontology resolution OWL species classification RDFS/OWL semantics validation general style evaluation domain specific style evaluation instance data referenced ontologies referenced ontologies URI or text of RDF document evaluation report optional ontologies optional ontologies