Enforcing Logically Weaker Knowledge in Classical Logic

This paper is concerned with a fundamental issue in knowledge representation and reasoning that, surprisingly, has received little attention so far. The point is that inserting some logically weaker (but, in a sense, more precise) information within a logic-based representation is not a straightforward process if the extra information must prevail. Indeed, it does neither prevail by itself nor disable the already existing logically stronger (but less precise) information that subsumes it. A general framework for solving this problem is introduced and instantiated to the task of making some rules prevail over more general ones.