Giovambattista Ianni Thomas Krennwallner Alessandra Martello Axel Polleres A Rule System for Querying Persistent RDFS Data. 857-862 2009 ESWC http://dx.doi.org/10.1007/978-3-642-02121-3_70 conf/esws/2009 db/conf/esws/eswc2009.html#IanniKMP09