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Owl

description:

  • OWL 2 ontologies themselves are primarily exchanged as RDF documents
    • i.e., the RDF-Based Semantics
    • but there's also direct semantics, looks like Declaration(Class(:Person))
  • OWL-Lite is the least expressive sub-langauge. OWL-Full is the most expressive sub-language. The expressiveness of OWL-DL falls between that of OWL-Lite and OWL-Full.

Semantics

  • The Direct Semantics [OWL 2 Direct Semantics] and the RDF-Based Semantics [OWL 2 RDF-Based Semantics] provide two alternative ways of assigning meaning to OWL 2 ontologies, with a correspondence theorem providing a link between the two.
    • The Direct Semantics assigns meaning directly to ontology structures, resulting in a semantics compatible with the model theoretic semantics of the SROIQ description logic

Highlights

  • OWL ontologies can use the preexisting OWL attribute owl:versionInfo to store version information.

Cons

  • since OWL does not have dynamic classification, a person will be classified as an employee regardless of whether they have a current or past employment. Temporal properties of the employment will reflect whether employment is past.
  • A second major feature that proves troublesome is the monotonic nature of the inheritance of imported information. The ability to import other ontologies is crucial to supporting reuse of information. But all such inheritance is monotonic—in other words, new information can be added, but none of the existing information can be retracted or overridden. This makes it imperative that one make sure that all assertions are made at the proper level in the inheritance structure. If assertions are added at too low a level, then no sharing takes place. If made too high up, then the information cannot be removed, which can limit the ability to share knowledge and settings. It is difficult, even for experienced users, to decide where new knowledge should be created.
    • The monotonic requirement also makes it impossible to have actual default values, since any such value could not be removed. We are able to avoid that problem through the use of meta-annotations that associate default values not with the individuals, but instead attach them to the properties themselves.
  • Why I Dont Use Owl Anymore

References

Children
  1. Manchester Syntax
  2. OWL 2 QL
  3. OWL Full
  4. OWL RL
  5. OWL-DL
  6. tOWL
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