Dimitris Plexousakis Querying and Viewing the Semantic Web: An RDF-Based Perspective. 60-61 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2932&spage=60 2004 conf/sofsem/2004 SOFSEM db/conf/sofsem/sofsem2004.html#Plexousakis04