Towards a knowledge level analysis of forgetting
James P. Delgrande · 2014
Forgetting has been addressed in various areas in KR, includ-ing classical logic, logic programming, modal logic, and de-scription logics. Here, we view forgetting as an abstract oper-ator, independent of the underlying logic. We argue that for-getting amounts to a reduction in the signature of a language of a logic, and that the result of forgetting elements of a sig-nature in a theory is the set of logical consequences over the reduced language. This definition offers several advantages. It provides a uniform approach to forgetting, applicable to any logic with a well-defined consequence relation. Obtained results are thus applicable to all subsumed formal systems, and typically are obtained much more straightforwardly. The approach also leads to insights with respect to specific logics: forgetting in first-order logic is somewhat different from the accepted approach; and the definition applied to logic pro-grams yields a new syntax-independent notion of forgetting.