Logic Programming and Nonmonotonic Reasoning 6th International Conference, LPNMR 2001, Vienna, Austria, September 17-19, 2001. Proceedings - Eiter, Thomas; Eiter, Thomas; Faber, Wolfgang; Faber, Wolfgang; Trusczynksi, Miroslaw; Trusczynksi, Miroslaw (Springer Berlin Heidelberg : Imprint: Springer, 2001)