introduction to description logics and owl n.
Skip this Video
Loading SlideShow in 5 Seconds..
Introduction to Description Logics and OWL PowerPoint Presentation
Download Presentation
Introduction to Description Logics and OWL

Loading in 2 Seconds...

play fullscreen
1 / 10

Introduction to Description Logics and OWL - PowerPoint PPT Presentation

  • Uploaded on

Introduction to Description Logics and OWL. Nick Gotts & Gary Polhill. What is an ontology?. “…a formal, explicit specification of a shared conceptualisation” [Gruber, 1993; Fensel, 2001] Formal: machine readable Explicit: types of concepts and constraints on their use

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

PowerPoint Slideshow about 'Introduction to Description Logics and OWL' - kendra

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
what is an ontology
What is an ontology?
  • “…a formal, explicit specification of a shared conceptualisation”[Gruber, 1993; Fensel, 2001]
    • Formal: machine readable
    • Explicit: types of concepts and constraints on their use
    • Shared: consensual knowledge accepted by a group
    • Conceptualisation: an abstract model
  • Essentially contain the following:
    • Classes of concept with declarative conditions for class membership
    • Relationships between classes

Gruber, T. R. (1993) Knowledge Acquisition 5, pp. 199-220.

Fensel, D. (2001) Ontologies: A Silver Bullet for Knowledge Management and Electronic Commerce. Springer

what can they do for caves
What can they do for CAVES?
  • CAVES: Not one model but many
    • One unifying ontology may not be possible or desirable
  • Comparison of ontologies of different case studies
  • Comparison of ontologies at different levels of granularity
  • Capturing relationships between ontologies
  • Higher-level descriptions of models that are nevertheless formal
owl and description logics
Owl and Description Logics
  • OWL (Web Ontology Language)
    • Allows ontologies to be published on the web
    • Allows ontologies to link to each other
    • One representation uses XML (via RDF)
    • Used in Protégé (ontology editor)
    • Conceptually linked to Description Logics
  • Description Logics
    • Origins
    • Some key properties
    • Reasoning within Description Logics.
    • Description Logics and the various versions of OWL.
  • Web Ontology Language
  • Relation to XML and RDF [CHECK!]
  • Origins and history
  • Formal languages with inference rules
  • Types of logic:
    • Propositional logic
    • First-order predicate logic
    • Higher-order predicate logics
    • Modal logics
    • Temporal logics
    • Description logics
  • Trade off: expressivity against computational tractability
description logics
Description Logics
  • Descended from AI approaches to knowledge representation (semantic nets, frames)
    • But with a formal, logic-based semantics
  • Concepts and roles
  • What sorts of things can be expressed in description logics? [EXAMPLES]
    • Description formalism
    • Terminological formalism
    • Assertional formalism
reasoning in description logics
Reasoning in Description Logics
  • Properties of Logics
    • Completeness
    • Decideability
  • Properties of algorithms for decideable logics:
    • Worst-case time complexity
    • Typical case / “In-practice” time complexity
  • Specialised automated reasoners for Description Logics: tableau-based algorithms
description logics as ontology languages
Description Logics as Ontology Languages
  • Several web ontology languages, including OWL, use the Description Logic SHIQ as basis of their design.
  • Ontologist-friendly features of SHIQ :
    • Qualified number restrictions
    • Complex terminological axioms
    • Inverse roles, transitive roles, subroles
  • Reasoning in SHIQ :
    • Decideable
    • Worst-case time-complexity exponential
    • Highly optimized SHIQ reasoners, e.g. RACER, behave quite well in practice
  • ?Extensions to SHIQ :
    • Concrete domains
    • Nominals
description of shiq
Description of SHIQ?
  • Tbox and Abox
  • Verifying the TBox (p.13)
  • Tableau-based decision procedure (p.16) “nondeterminisitc double exponential time” [!?!]