Jos de Bruijn Stijn Heymans Logical Foundations of (e)RDF(S): Complexity and Reasoning. 86-99 2007 conf/semweb/2007 ISWC/ASWC http://dx.doi.org/10.1007/978-3-540-76298-0_7 db/conf/semweb/iswc2007.html#BruijnH07