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The OWL specification is maintained by the World Wide Web Consortium (W3C).

OWL currently has three flavors: OWL Lite, '''OWL DL''', and '''OWL Full'''.
These flavors incorporate different Feature s, and in general it is easier to reason about OWL Lite than OWL DL and OWL DL than OWL Full. OWL Lite and OWL DL are constructed in such a way that every statement can be decided in finite time; OWL Full can contain endless 'loops'.


HISTORY


OWL DL is based on the Description Logic \mathcal{SHOIN} (D).
Its subset OWL Lite is based on the less expressive logic \mathcal{SHIF} (D).


SUBLANGUAGES


OWL provides three increasingly expressive sublanguages designed for use by specific communities of implementers and users.

  • ''OWL Lite'' supports those users primarily needing a classification hierarchy and simple constraints. For example, while it supports Cardinality constraints, it only permits cardinality values of 0 or 1. It should be simpler to provide tool support for OWL Lite than its more expressive relatives, and OWL Lite provides a quick migration path for thesauri and other taxonomies. Owl Lite also has a lower formal complexity than OWL DL, see the section on OWL Lite in the OWL Reference for further details.


  • ''OWL DL'' supports those users who want the maximum expressiveness while retaining Computational Completeness (all conclusions are guaranteed to be computed) and Decidability (all computations will finish in finite time). OWL DL includes all OWL language constructs, but they can be used only under certain restrictions (for example, while a class may be a subclass of many classes, a class cannot be an instance of another class). OWL DL is so named due to its correspondence with Description Logic , a field of research that has studied the logics that form the formal foundation of OWL.


  • ''OWL Full'' is meant for users who want maximum expressiveness and the syntactic freedom of RDF with no computational guarantees. For example, in OWL Full a class can be treated simultaneously as a collection of individuals and as an individual in its own right. OWL Full allows an ontology to augment the meaning of the pre-defined (RDF or OWL) vocabulary. It is unlikely that any reasoning software will be able to support complete reasoning for every feature of OWL Full.


Each of these sublanguages is an extension of its simpler predecessor, both in what can be legally expressed and in what can be validly concluded. The following set of relations hold. Their inverses do not.

  • Every legal OWL Lite ontology is a legal OWL DL ontology.

  • Every legal OWL DL ontology is a legal OWL Full ontology.

  • Every valid OWL Lite conclusion is a valid OWL DL conclusion.

  • Every valid OWL DL conclusion is a valid OWL Full conclusion.



THE ACRONYM


Some may claim that the correct acronym for ''Web Ontology Language'' should be ''WOL'' instead of ''OWL''. Others believe that
the order was chosen in honor of the character Owl from Winnie The Pooh , who wrote his name WOL instead of OWL. In truth, OWL was proposed as an acronym that would be easily pronounced, yield good logos, suggest wisdom and honor Bill Martin's ''One World Language'' KR project from the 1970s. And, quoting Guus Schreiber: ''Why not be inconsistent in at least one aspect of a language which is all about consistency.''


SEE ALSO



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