, PaulErdoes) . creator(X,Y) Returns the persons and the papers that were written with Paul Erdoes

, Article) . journal(X,Journal1-1940) . creator(X,Y) Returns the creators of all the elements that are articles and were, Journal, vol.1, 1940.

, Article) . creator(X,PaulErdoes) Returns all the articles created by Paul Erdoes

F. Baader, S. Brandt, and C. Lutz, Pushing the el envelope, Proc. of IJCAI 2005, 2005.

D. Calvanese, G. De-giacomo, D. Lembo, M. Lenzerini, and R. Rosati, Tractable reasoning and efficient query answering in description logics: The dl-lite family, J. Autom. Reasoning, vol.39, issue.3, pp.385-429, 2007.

B. Haslhofer, E. M. Roochi, B. Schandl, and S. Zander, Europeana RDF store report, 2011.

M. Lenzerini, Data integration: A theoretical perspective, Proc. of PODS 2002, 2002.

M. Schmidt, T. Hornung, G. Lausen, and C. Pinkel, Sp2bench: A sparql performance benchmark, 2008.