Extensible Ontological Modeling Framework for Subject Mediation

1. Extensible Ontological Modeling Frameworkfor Subject Mediation L. A. Kalinichenko, N. A. Skvortsov Institute for Problems of Informatics, RAS {leonidk,scvora}@synth.ipi.ac.ru http://www.ipi.ac.ru/synth/ RCDL’2002, Dubna

2. Outline • An approach for the ontological model mapping in a subject mediation environment intended for heterogeneous information sources integration in a particular subject domain is considered. Such mapping is needed for an information source registration at the mediator. It is assumed that such sources apply the DAML+OIL ontological model. A mediator ontological language (MOL) may depend on a subject domain and is to be defined at the mediator consolidation phase. • Principles of information resource registration. • Ontological framework of subject mediators. • Mapping of DAML+OIL elements into MOL ones. • Reverse mapping

3. Registration of resources in subject mediator • Canonical model of the the mediator used for information resource specifications • Mediators work in consolidation phase, then in operational phase • Specification modules: schemas, concept definitions, vocabularies • Local as View (LAV) mediator architecture is assumed as a basis for the subject mediation • For this purpose source specifications are mapped to federative level of mediator specifications

4. Mediator’s Ontological Framework • the same canonical model used for specifications of ontological contexts of mediator and of information sources • Elements of specifications are concepts, attributes, associations, invariants • Also semantic relationships that may be fuzzy • To contextualize information sources at the mediator during their registration, it is required to map local ontological contexts of the sources into the mediator’s ontology. • loose ontological integration provides for establishing fuzzy correlation between related concepts • tight ontological integration consists in composition of ontological modules using complete specifications of concepts as type definitions

5. DAML+OIL • DAML+OIL layered on top of RDFS • Classes (concepts) and properties (roles) • DAML+ OIL ontology consists of set of axioms asserting characteristics of classes and properties • Equivalent to very expressive description logic SHIQ • Reasoning algorithms for satisfiability and subsumption (it may be used for tight ontology integration) • DAML+OIL has been submitted to W3C as a candidate for the Web ontology language • Class constructors: intersectionOf, unionOf, complementOf, oneOf, toClass, hasClass, hasValue, minCardinalityQ, maxCardinalityQ, cardinalityQ • Axioms: subClassOf, sameClassAs, subPropertyOf, samePropertyAs, sameIndividualAs, disjointWith, differentIndividualFrom, inverseOf

6. Core of the Mediator Ontology Language (1) • Types (concepts) • Attributes • Invariants { Animal; in: type, daml_oil; hasMother: Female; metaslot in: HasMother; end sameAs: {in: invariant, samePropertyAs, {{ all a/Animal ( hasMother(a) = HasMom(a) }}} }

7. Core of the Mediator Ontology Language (2) • Association types { HasFather; in: metatype, association, daml_oil; instance_section: { domain: Animal; range: Male; association_type: {{1,1},{0,inf}}; metaslot in: onProperty, cardinality, UniqueProperty, end} };

8. MOL core extension equivalent to DAML+OIL (1) • Need in new metaclasses • daml_oil: types and associations become instances of the metatype; • restriction: belonging to it are restrictions of DAML+OIL; • disjointWith, disjointUnionOf, onProperty, toClass, hasValue, hasClass, cardinality, maxCardinality, minCardinality, cardinalityQ, maxCardinalityQ, minCardinalityQ, sameTypeAs, equivalentTo, samePropertyAs: metatypes to which invariants in type definitions can be associated. These invariants interpret respective DAML+OIL elements.

9. MOL core extension equivalent to DAML+OIL (2) • Class Elements Interpretation I: {in: invariant, disjointWith, {{(C>T1 & CE>T2 = {}) }}} I: {in:predicate, invariant, disjointUnionOf, {{(C>T = (CE1>T1 | CE2>T2)) & (CE1>T1 & CE2>T2 = {}) }}} I: {in: invariant, sameClassAs, {{(C>T1 = CE>T2)}}} { HumanBeing; in: type, daml_oil; supertype: Person; sameTypeAs: {in: invariant, sameClassAs {{all p/Person (HumanBeing(p) = Person(p)) }}} };

10. MOL core extension equivalent to DAML+OIL (3) • Property Restrictions Interpretation I: {in: invariant, onProperty, toClass, {{all x (ST(x) & (P(x)  CE>T))}}} I: {in: invariant, onProperty, hasValue, {{all x (ST(x) & yP(x)) }}} I: {in: invariant, onProperty, hasClass, {{all x (ST(x) & ex y (P(x,y) & CE>T(y))) }}} { R_Person; in: type, daml_oil, restriction;supertype: Animal; hp: {in: invariant, onProperty, toClass, {{all ap (R_Person(ap) & hasParent(ap) <= Person) }}}; };

11. MOL core extension equivalent to DAML+OIL (4) • Cardinality Constraints Interpretation daml:cardinality -> association_type: {{N,N},{?,?}} daml:maxCardinality -> association_type: {{0,N},{?,?}} daml:minCardinality -> association_type: {{N,inf},{?,?}} { domain: C>T1; range: CE>T2; association_type: {{N,N},{?,?}}; metaslot in: onProperty, cardinalityQ end } or I: {in: invariant, onProperty, cardinalityQ, {{all x(C>T1(x) & count (P(x) & CE>T2) = N) }}}

12. Reverse Mapping of the MOL into DAML+OIL • The mapping is reversible • Semantics of any DAML+OIL definition mapped to MOL is retrievable using newly defined metaclasses • DAML+OIL specifications are extended by RDF namespace to save semantics of fuzzy semantic relationships in MOL { Female; in: type, daml_oil; supertype: Animal; disjoint: {in: invariant, disjointWith, {{Male(a/Animal) & Female(a/Animal) = {} }}} }; <daml:Class rdf:ID="Female"> <rdfs:subClassOf rdf:resource="#Animal"/> <daml:disjointWith rdf:resource="#Male"/> </daml:Class>

13. Conclusion • Compatibility to most popular ontologies and probable W3C recommendation for Web ontologies • Results may be used for mapping other ontologies • SHIQ reasoning algorithms are helpful for tight ontology integration