Good answer. Nice to see the original questioner accepted it. To take it a bit further, so-called "answer set solvers" like clasp (http://potassco.sourceforge.n

Good answer. Nice to see the original questioner accepted it. To take it a bit further, so-called "answer set solvers" like clasp (http://potassco.sourceforge.net/ http://potassco.sourceforge.net/) provide a fast way to run these kinds of logic programs.