François Bry Norbert Eisinger Thomas Eiter Tim Furche Georg Gottlob Clemens Ley Benedikt Linse Reinhard Pichler Fang Wei Foundations of Rule-Based Query Answering. 1-153 2007 conf/rweb/2007 Reasoning Web http://dx.doi.org/10.1007/978-3-540-74615-7_1 db/conf/rweb/rweb2007.html#BryEEFGLLPW07