"Abduction" is sometimes used to mean just the generation of hypotheses to explain observations or conclusionsm, but the former definition is more common both in philosophy and computing.
The semantics and the implementation of abduction cannot be reduced to those for deduction, as explanation cannot be reduced to implication.
Applications include fault diagnosis, plan formation and default reasoning.
Negation as failure in logic programming can both be given an abductive interpretation and also can be used to implement abduction. The abductive semantics of negation as failure leads naturally to an argumentation-theoretic interpretation of default reasoning in general.
[Better explanation? Example?]
["Abductive Inference", John R. Josephson <email@example.com>].