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An OWL library for [SWI] Prolog

Thea is a Prolog library for generating and manipulating OWL (Web Ontology Language) content. Thea version 0.5 consists of:

  • OWL parser,

  • OWL generator and

  • SQL to OWL converter.

Current version of Thea OWL Prolog library (v 0.5) released April 21, 2006.

Next version of Thea that will support OWL2, is currently in early development state: Thea2 project is hosted on GitHUB


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

Thea OWL generator is used to the OWL absract sysntax constructs from Prolog terms into RDF triples and saving the resulting RDF model into an RDF/XML file. Thea OWL generator is also using SWI-Prologs Semantic Web library for saving RDF models into RDF/XML files.

Thea SQL to OWL converter is used to generate OWL facts from records in a relational database. SQL2OWL uses SWI-Prolog’s ODBC package to access the RDBMS. The conversion is guided by a mapping between Relational entities (Tables and Columns) and OWL constructs (Classes and Properties). The mapping is defined in a declarative form by means of Prolog terms.

Downloads - Demo

Thea OWL Lib is available under the GNU/GPL license.

Latest version

  • Thea OWL Lib v0.5.

    The package contains the SQL to OWL mappings used in the documentation as well as a MySQL dump of the database used in the documentation examples.

Previous versions


Thea OWL is a project of SemanticWeb.gr. For any questions, comments and suggestions please contact:

Vangelis Vassiliadis