Henrik Nottelmann PIRE: An Extensible IR Engine Based on Probabilistic Datalog. 260-274 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3408&spage=260 2005 conf/ecir/2005 ECIR db/conf/ecir/ecir2005.html#Nottelmann05