Non-monotonic logic  From Wikipedia, the free encyclopedia Jump
to: navigation, search  A non-monotonic logic is a formal logic
whose consequence relation is not monotonic. Most studied formal
logics have a monotonic consequence relation, meaning that
adding a formula to a theory never produces a reduction of its
set of consequences. Intuitively, monotonicity indicates that
learning a new piece of knowledge cannot reduce the set of what
is known. A monotonic logic cannot handle various reasoning
tasks such as reasoning by default (consequences may be derived
only because of lack of evidence of the contrary), abductive
reasoning (consequences are only deduced as most likely
explanations), some important approaches to reasoning about
knowledge (the ignorance of a consequence must be retracted when
the consequence becomes known), and similarly, belief revision
(new knowledge may contradict old beliefs).  Abductive
reasoning[edit]   Reasoning about knowledge[edit]   Belief
revision[edit]   Proof-theoretic versus