Web Ontology Language (OWL). CS590SW: Semantic Web (Winter Quarter 2003) Presentation: Michael Eckert. What is OWL?. Motivation:.
CS590SW: Semantic Web(Winter Quarter 2003)Presentation: Michael Eckert
“Computational Agents require machine-readable descriptions of the content and capabilities of web accessible resources. These descriptions must be in addition to the human-readable versions of the information.”
“Ontologies facilitate greater machine readability of web content than XML, RDF, and RDF-S by providing additional vocabulary for term descriptions.”
“The Web Ontology Language (OWL) is intended to provide a language that can be used to describe the classes and relations between them that are inherent in Web documents and applications”
OWL can be used to Formalize a domain by defining classes and properties of those classes Define individuals and assert properties about them Reason about these classes and individuals to the degree permitted by the formal semantics of the OWL language
W3C’s Architecture for a Semantic Web
Web Ontology Language (OWL)
RDF + rdfschema
XML + NS + xmlschema
Restriction of the expressiveness of First Order Logic (usually to the degree of PSPACE-completeness) Semantic: set-theoretic interpretation Concepts (Sets), Roles (binary Relations), Individuals (Elements) Various Operators and Quantifiers T(erminological)-Box: definitions and axioms A(ssertional)-Box: information about individuals Note: names of individuals can be used in a T-Box e.g. open world assumption, no unique naming assumtion
Defining classes: Class
<owl:Class rdf:ID=“Region” />
<owl:Class rdf:ID=“PotableLiquid” />
Building class hierarchies: subClassOf
datatype properties: binary relation between elements of classes and XML datatypes
object properties: binary relation between elements of two classes
<owl:ObjectProperty rdf:ID=“producedIn” />
Form Classes using class expressions.
Set Operators intersectionOf, unionOf, complementOf Enumerated Classes: oneOfDefine a class via enumeration of its members closes class extension Disjoint Classes: disjointWith Set of mutually disjoint classes: one disjointWith assertion per pair
Are given in the property definition and apply globally to all instances of the property. Their specification provides a powerful mechanism for enhanced reasoning about a property.
Specification of domain and range subPropertyOf TransitiveProperty, SymmetricProperty FunctionalProperty, InverseFunctionalProperty (“unique key”) inverseOf
OWL: Property Restrictions
Are given in a class definition and apply only locally to their containg class.
Quantifiers: allValuesFrom, someValuesFrom Cardinality:cardinality, minCardinality, maxCardinality Relate individuals as particular property values to class: hasValue
OWL supports RDF’s namespace mechanism and allows to importing other ontologies into the current knowledgebase via imports.To support effective sharing and reuse of ontologies we additionally need ways to identify correspondences between two ore more ontologies:
Equivalency: sameClassAs, samePropertyAs Identity - Dealing with the no unique naming assumption:sameIndividualAs, differentIndividualFrom
OWL builds upon XML and RDS
Three increasingly complex languages: OWL Lite, OWL DL, OWL Full
Theoretical foundation: Description Logics
Classes, Properties, Individuals
Reasoning: Property Characteristics, Restrictions, Complex classes
Reuse of Ontologies: Ontology Mapping
W3C Sematic Web: http://www.w3.org/2001/sw/ Web Ontology Language (OWL) Guide Version 1.0http://www.w3.org/TR/owl-guide/ Alexander Borgida: Description Logics in Datamanagement TKDE 7(5):671-682 (1995).