Thea: A Web Ontology Language - OWL Parser for [SWI] Prolog.


Vangelis Vassiliadis



Thea is a Prolog implementation of an OWL parser. Thea uses SWI-Prolog’s Semantic Web library for parsing RDF/XML serialisations of OWL documents into RDF triples and then it builds a representation of the OWL ontology as it is defined in the OWL Web Ontology Language Semantics and Abstract Syntax part of the OWL specification. The OWL ontology abstract syntax is implemented as Prolog terms. 


Thea is a project of and is available under the GNU/GPL license.

Current version of Thea OWL parser (v 0.3) released March 22, 2005.


Thea has been tested extensively against the OWL test cases and for almost all cases it generates the correct syntactic constructs.

Known issues and limitations:

-         Thea v.0.3 is not a reasoner: it does not make any inferences nor it checks the consistency of the resulted OWL ontology.

-         Thea parses all ‘versions’ of OWL ontologies (Full/DL/Lite) but does it is not currently a ‘species’ validator.

-         No support for the owl:import directive: any ‘imported’ ontology is not parsed automatically.

-         There is limited datatype support (SWI Prolog RDF parser’s current implementation has no provisions for XML-Schema typed literals).

-         The owl:equivalentProperty axiom is not supported.

-         The value of an individual is not tested for structure sharing.



Thea OWL Parser for SWI Prolog library



Please send me any comments and suggestions.