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DAML+OIL: an Ontology Language for the Semantic Web

DAML+OIL: an Ontology Language for the Semantic Web. DAML+OIL Design Objectives. Well designed Intuitive to (human) users Adequate expressive power Support machine understanding/reasoning Well defined Clearly specified syntax (obviously) Formal semantics (equally important)

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DAML+OIL: an Ontology Language for the Semantic Web

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  1. DAML+OIL: an Ontology Language for the Semantic Web

  2. DAML+OIL Design Objectives • Well designed • Intuitive to (human) users • Adequate expressive power • Support machine understanding/reasoning • Well defined • Clearly specified syntax (obviously) • Formal semantics (equally important) • Extend existing web standards • DAML+OIL is built on top of RDF(S)

  3. Why Build on RDF • Provides basic ontological primitives • Classes and relations (properties) • Class (and property) hierarchy • Can exploit existing RDF infrastructure • Provides mechanism for using ontologies • RDF triples assert facts about resources • Use vocabulary from DAML+OIL ontologies

  4. DAML+OIL DC PICS XHTML SMIL RDF(S) HTML XML The Cake!

  5. Why RDF Is Not Enough • Expressive inadequacy • Only range/domain constraints (on properties) • No properties of properties (unique, transitive, inverse etc.) • No equivalence, disjointness, coverings etc. • No necessary and sufficient conditions (for class membership) • Poorly (un) defined semantics

  6. How DAML+OIL Builds ON RDFS (1) • Extends expressive power • Constraints (restrictions) on properties of classes (existential/universal/cardinality) • Boolean combinations of classes and restrictions • Equivalence, disjointness, coverings • Necessary and sufficient conditions • Constraints on properties

  7. How DAML+OIL Builds ON RDFS (2) • Provides well defined semantics • Meaning of DAML+OIL statements is formally specified • Both model theoretic and axiomatic specifations provided • Allows for machine understanding and automated reasoning

  8. DAML+OIL  RDF • DAML+OIL ontology is a set of RDF statements • DAML+OIL defines semantics for certain statements • Does NOT restrict what can be said • Ontology can include arbitrary RDF • But no semantics for non-DAML+OIL statements

  9. Well Designed(?) • Intuitive to (human) users • Supports common ontological idioms • Adequate expressive power • Extends RDF in several directions • Support for machine understanding/reasoning • Designed to be “implementable” • No features for which it is difficult or impossible to define clear semantics (e.g., defaults) • Decidable and (empirically) tractable reasoning

  10. Why Automated Reasoning? • Semantic web requires machine understanding (of resource descriptions) • Reasoning is integral to understanding • Supports design and use of ontologies • Checking class consistency (e.g., Skyscraper) • Checking/deriving subClassOf hierarchy • Particularly useful when ontologies are large, multi-authored and rapidly evolving • Also useful when integrating/sharing ontologies • Does not tell us how to deal with inconsistencies • But we should be able to determine when they exist

  11. Extending DAML+OIL • Work in progress on Datatypes • Plan to support (some of) XMLS datatypes • Datatypes will be disjoint from “abstract” classes and only accessible via properties • Maintains “implementability” of language • Further extensions in new language layers • E.g., DAML-RULES • Layers will use DAML+OIL as it uses RDF

  12. New Language Layers DAML-??? DAML+OIL DC PICS XHTML SMIL RDF(S) HTML XML

  13. DAML+OIL Infrastructure • Can exploit existing RDF tools/services • Ontology editors being built/adapted • OilEd (Manchester) • Protégé (Stanford) • OntoEdit (Karlsruhe) • Ontology integration tools being built/adapted • Chimera (Stanford) • Reasoning services • DL derived reasoners, e.g., FaCT (used by OilEd) • Rule based reasoners, e.g. SiLri (Karlsruhe) • Markup tools • Additional tools/infrastructure urgently required

  14. DAML+OIL Summary • Ontology language for Semantic Web • Extends RDF • More expressive power • Well defined semantics • Implementable • Decidable and tractable reasoning • Cost is some restriction on expressive power • Extensible • Cost may be loss of (some of) above properties

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