Laks V. S. Lakshmanan Fereidoon Sadri 146-163 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2870&spage=146 2003 conf/semweb/2003 International Semantic Web Conference db/conf/semweb/iswc2003.html#LakshmananS03