The Stable Model Semantics for Logic Programming (1988)
Michael Gelfond and Vladimir Lifschitz
We propose a new declarative semantics for logic programs with negation. Its formulation is quite simple; at the same time, it is more general than the iterated fixed point semantics for stratified programs, and is applicable to some useful programs that are not stratified.
In Proceedings of International Logic Programming Conference and Symposium, Kowalski, Robert and Bowen, Kenneth (Eds.), pp. 1070-1080 1988. MIT Press.

Vladimir Lifschitz Faculty vl [at] cs utexas edu