06 Dec Rev. 14 Dec CmpE 583 Fall 2008 OWL Language 1 OWL Language off Lacy Ch. 10 Atilla Elçi

06 Dec Rev. 14 Dec CmpE 583 Fall 2008 OWL Language 2 What is OWL? Language to support the Semantic Web Logical layer in SemWeb architecture Based on RDFS; and, further extends it Has additional language features for describing ontologies W3C’s recommended ontology language for representing information in the SemWeb.

06 Dec Rev. 14 Dec CmpE 583 Fall 2008 OWL Language 3 OWL History DARPA Agent Markup Language (DAML): –DARPA research program: 2000 Obj.: interoperability among (US Fed Gov) DoD IT systems. Dr. James Handler (U. of Maryland) initiated. Murray Burke & later Dr. Mark Greaves MIT took part. European Project: Ontology Interface Layer (OIL) Joint EU/US committee on OIL merged the two in 2001: DAML+OIL DAML+OIL: –To define ontologies for communicating agents –A thin layer on top of RDFS –Starting of W3C Web Ontology Working Group of W3C Semantic Web Activity: Dr. James Handler & Dr. Guus Schreiber Obj.: Describing expressive semantics: A formal semantics to precisely define the meaning of expressions and valid inferences from them. Outcome is OWL. OWL: adopted as W3C recommendation on February 10, 2004.

06 Dec Rev. 14 Dec CmpE 583 Fall 2008 OWL Language 4 OWL Definition: Recommendations OWL authoriative description: all dated Feb.10, OWL Overview: Provides an OWL introductionOWL Overview OWL Guide: Demonstrates the use of OWL with examplesOWL Guide OWL Reference: Structured informal introduction to OWL constructsOWL Reference OWL Semantics and Abstract Syntax: Provides the normative (that is, official) definition of OWLOWL Semantics and Abstract Syntax OWL Test Cases: Provides test cases for OWLOWL Test Cases OWL Use Cases and Requirements: Specifies usage scenarios, goals and requirementsOWL Use Cases and Requirements

06 Dec. 2006CmpE 583 Fall 2008 OWL Language 5 OWL Definition: namespace Recommended namespace prefix: –owl Namespace URI: – MIME type: –Application/rdf+xml

06 Dec. 2006CmpE 583 Fall 2008 OWL Language 6 OWL Flavors (dialects, species, variants) OWL comes in three flavors in order to support different groups of users needing varying levels of expressional capability : OWL Lite: –A simple sublanguage of OWL Full: minimal set of features –Has a subset of OWL Full features; even some are restricted –For transition from DB, XML, or RDF(S) information representation to ontology use –Supports efficient reasoning –Requires much simpler tools than DL / Full. OWL DL: –A Description Language variant of OWL Full –Uses OWL Full constructs but restricts usage of some of them –Restrictions render OWL DL as decidable: => computaitons will finish in a finite amount of time –Obj.: to support reasoning applications. OWL Full: –The complete OWL Language –Superset of RDF –No restrictions on RDF doc.