- 1 - on Knowledge Evolution : Acquisition , Revision , Contraction

We consider evolution of Knowledge Bases caused by a sequence of basic steps of acquisition of a new information, either consistent or inconsistent with the original system. To make this process comply with the Principle of Minimal Change, a special evidence metric is introduced for measuring distance between states of knowledge. Then a novel semantics of knowledge bases is developed suggested by the heuristics of weighted maximally consistent subsets . The latter is efficiently applied to the processes of consistent and inconsistent acquisition of knowledge, belief revision and contraction.