Abstract

In this paper, we investigate the rules that should underlie a computer program that is capable of revising its beliefs or opinions. Such a program maintains a model of its environment, which is updated to reflect perceived changes in the environment. This model is stored in a knowledge base, and the program draws logical inferences from the information in the knowledge base. All the inferences drawn are added to the knowledge base. Among the propositions in the knowledge base, there are some in which the program believes, and there may be others in which the program does not believe. Inputs from the outside world or reasoning carried out by the program may lead to the detection of contradictions, in which case the program has to revise its beliefs in order to get rid of the contradiction and to accommodate the new information