Default Logic
Default logic is a non-monotonic logic proposed by Raymond Reiter to formalize reasoning with default assumptions. Default logic can express facts like “by default, something is true”; by contrast, standard logic can only express that something is true or that something is false. This is a problem because reasoning often involves facts that are true in the majority of cases but not always. (http://en.wikipedia.org/wiki/Default_logic)
Success of Default Logic 1999
Vladimir Lifschitz, In Logical Foundations for Cognitive Agents: Contributions in Honor of Ray Reiter, Levesque, Hector and Pirri, Fiora (Eds.), pp. 208-212 1999. Springer.
Update by Means of Inference Rules 1997
Teodor Przymusinski and Hudson Turner, Journal of Logic Programming, Vol. 30, 2 (1997), pp. 125-143.
Minimal Belief and Negation as Failure 1994
Vladimir Lifschitz, Artificial IntelligenceGabbay, D.M. and Hogger, C.J. and Robinson, J.A. (Eds.), Vol. 70 (1994), pp. 53--72. Oxford University Press.
Disjunctive Defaults 1991
Michael Gelfond, Vladimir Lifschitz, Halina Przymusinska and Miroslaw Truszczynski, In Proceedings of International Conference on Principles of Knowledge Representation and Reasoning (KR), Allen, James and Fikes, Richard and Sandewall, Erik (Eds.), pp. 230-237 1991.
On Open Defaults 1990
Vladimir Lifschitz, In Computational Logic: Symposium Proceedings, Lloyd, John (Eds.), pp. 80-95 1990. Springer.