@inproceedings{DBLP:conf/pods/CaliGL09,
  title = "A General Datalog-Based Framework for Tractable Query Answering over Ontologies",
  author = "Andrea Cal\`{\i} and Georg Gottlob and Thomas Lukasiewicz",
  year = "2009",
  booktitle = "Proceedings of the 28th ACM Symposium on Principles of Database Systems, PODS 2009, Providence, Rhode Island, USA, June 19 - July 1, 2009",
  editor = "Jan Paredaens and Jianwen Su",
  isbn = "978-1-60558-553-6",
  pages = "77-86",
  publisher = "ACM Press",
  url = "http://dl.acm.org/citation.cfm?doid=1559795.1559809",
}