From SHIQ and RDF to OWL: The Making of a Web Ontology Language

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From SHIQ and RDF to OWLThe Making of a Web
Ontology Language

• Ian Horrocks Peter F. Patel-Schneider and Frank
  van Harmelen
• Presented by Zonghui Lian

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Ontology Languages

• So far, how many ontology languages we can know
• XOL (XML-based Ontology Exchange Language)
• SHOE (Simple HTML Ontology Extension)
• OML (Ontology Markup Language)
• RDF(S) (Resource Description Framework (Schema))
• OIL (Ontology Interchange Language)
• DAMLOIL (DARPA Agent Markup Language OIL)
• OWL (Ontology Web Language)

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XML XML Schema

• XML provides a standardized syntactical way to
  expose structural information
• XML schema allows to define a schema for XML
  documents and may already provide
  machine-understandable semantics of data
• Do not attach meaning to structural information

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RDF Schema

• RDFS is too weak to describe resources in
  sufficient detail
• No localised range and domain constraints
• For example, cant express such a subclass of
  person the person who has children.
• No existence/cardinality constraints
• Cant say that all instances of person have a
  mother that is also a person, or that persons
  have exactly 2 parents
• No transitive, inverse or symmetrical properties
• Cant say that isPartOf is a transitive property,
  that hasPart is the inverse of isPartOf or that
  touches is symmetrical
• Difficult to provide reasoning support

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Requirements

• Desirable features identified for a Web Ontology
  Language
• Compatible with existing Web standards (XML,
  RDF, RDFS)
• Easy to understand and use
• Formally specified
• Has adequate expressive power
• Tools for reasoning support

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Layers of Languages
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OWL (Ontology Web Language)

• OWL is now a W3C Recommendation
• The purpose of OWL is identical to RDFS i.e. to
  provide an XML vocabulary to define classes,
  properties and their relationships.
• RDFS enables us to express basic relationships
  and has limited inferencing capability.
• OWL enables us to express much richer
  relationships, thus yielding a much enhanced
  inferencing capability.
• The benefit of OWL is that it facilitates a much
  greater degree of inferencing than you get with
  RDF Schema.

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Comparison RDF and OWL
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Introduction of OWL (Ontology Web Language)

• Description logic and frames
• Many characteristics of RDF

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D.Ls Influence on OWL

• Semantics are well defined.
• OWL uses D.L model theory to formalise the
  meaning of the language.
• Advantages

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D.Ls Influence on OWL

• Language constructors
• Expressive power
• Class (property) constructors
• Axioms
• Conflict with the computational complexity
• OWL entailment
• Blance

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D.Ls Influence on OWL

• Datatypes
• Difference with
• Advantage
• Decrease the complexity easy to answer question
• -5 nonNegative ?

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Origins of OWL
DARPA Agent Markup Language
Ontology Inference Layer
DAML
OIL
RDF
EU/NSF Joint Ad hoc Committee
DAMLOIL
All influenced by RDF
OWL Lite OWL DL OWL Full
A W3C Recommendation
OWL
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Versions of OWL

• Depending on the intended usage, OWL provides
  three increasingly expressive sublanguages

OWL Full

• Full Consider the compatibility with RDF and
  RDFS as the primary importance. no computation
  guarantees
• DL (Description Logic) Friendly syntax,
  decidable inference. computationally complete
• Lite Simpler syntax and more tractable
  inference.

OWL DL
OWL Lite
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Advantages/Disadvantages of versions

• Full
• The advantage of the Full version of OWL is that
  we get the full power of the OWL language.
• The disadvantage is that it is very difficult to
  build a computational tool for this version and
  may not get a quick and complete answer.
• DL/Lite
• The advantage of the DL or Lite version of OWL is
  that tools can be built more quickly and easily,
  and users can expect responses from such tools to
  come quicker and be more complete.
• The disadvantage is that we don't have access to
  the full power of the language.

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OWL as D.L
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OWL as D.L
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Conclusion

• Difference b/w OWL DL D.L
• Datatyping mechanisms (XML schema datatypes)
• RDF URI reference as name
• Entailments OWL DL is compatible with that of RDF
  and RDFS