Enrico Franconi Sergio Tessaris Rules and Queries with Ontologies: A Unified Logical Framework. 50-60 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3208&spage=50 2004 conf/ppswr/2004 PPSWR db/conf/ppswr/ppswr2004.html#FranconiT04