Dennis P. Groth An Evaluation of a Rule-Based Language for Classification Queries. 79-97 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3392&spage=79 2004 conf/wlp/2004 INAP/WLP db/conf/wlp/wlp2004.html#Groth04