Ontology on PostgreSQL - is there something?

Dear PG-hackers,<br /><br />Based on the paper below [1], I ask: is there anyone working on, or already tried to such
nativeimplementation on PostgreSQL? I didn't find anything related on pgFoundry. There is also a presentation [2]
relatedto the paper. <br /><br /><span class="bodycopy" style="font-style: italic;">"By Souripriya Das, Eugene Inseok
Chong,George Eadon, Jagannathan Srinivasan, Proceedings of the 30th VLDB Conference, Toronto, Canada. Ontologies are
increasinglybeing used to build applications that utilize domain-specific knowledge. <span style="text-decoration:
underline;">Thispaper addresses the problem of supporting ontology-based semantic matching in RDBMS.</span> The
approachenables users to reference ontology data directly from SQL using the semantic match operators, thereby opening
uppossibilities of combining with other operations such as joins as well as making the ontology-driven applications
easyto develop and efficient. In contrast, other approaches use RDBMS only for storage of ontologies and querying of
ontologydata is typically done via APIs. This paper presents the ontology-related functionality including inferencing,
discusseshow it is implemented on top of Oracle RDBMS, and illustrates the usage with several database
applications."</span><spanclass="legalese" style="font-style: italic;"></span><br clear="all" style="font-style:
italic;"/><br />[1] <a href="http://www.cs.toronto.edu/vldb04/protected/eProceedings/contents/pdf/IND3P1.PDF">
http://www.cs.toronto.edu/vldb04/protected/eProceedings/contents/pdf/IND3P1.PDF</a><br/>[2] <a
href="http://www-scf.usc.edu/~csci586/ppt-2005/dguo.pps">http://www-scf.usc.edu/~csci586/ppt-2005/dguo.pps</a><br/><br
/>Besides,what are your opinions on the subject? <br /><br />Is it worthful to have such native implementation on PG,
evenas a modest contrib module?<br />Based on your development know-how on the backend internals, how difficult is it
todevelop this (3 operators + 1 index type)? <br /><br />-- <br />Best regards,<br /><br />Rodrigo Hjort<br /><a
href="http://icewall.org/~hjort">http://icewall.org/~hjort</a><br/>CELEPAR - Cia de Informática do Paraná - Brasil<br
/><ahref="http://www.pr.gov.br">http://www.pr.gov.br </a><br /><br />