Semantical considerations on nonmonotonic logic
Artificial Intelligence
Possible-world semantics for autoepistemic logic
Readings in nonmonotonic reasoning
On the relation between default and autoepistemic logic
Artificial Intelligence
General theory of cumulative inference
Proceedings of the 2nd international workshop on Non-monotonic reasoning
Theoretical foundations for non-monotonic reasoning in expert systems
Logics and models of concurrent systems
Nonmonotonic Logic II: Nonmonotonic Modal Theories
Journal of the ACM (JACM)
Intuitonistic Basis for Non-Monotonic Logic
Proceedings of the 6th Conference on Automated Deduction
AAAI'92 Proceedings of the tenth national conference on Artificial intelligence
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Conclusions by failure to prove the opposite are frequently used in reasoning about an incompletely specified world. This naturally leads to logics for default reasoning which, in general, are nonmonotonic, i.e., introducing new facts can invalidate previously made conclusions. Accordingly, a nonmonotonic theory is called (nonmonotonically) degenerate, if adding new axioms does not invalidate already proved theorems. We study nonmonotonic logics based on various sets of defaults and present a necessary and sufficient condition for a nonmonotonic modal theory to be degenerate. In particular, this condition provides several alternative descriptions of degenerate theories. Also we establish some closure properties of sets of defaults defining a nonmonotonic modal logic.