On Syntactic Forgetting with Strong Persistence

Abstract

It is generally agreed upon that so-called strong persistence (SP) captures best the essence of forgetting in logic programming. While classes of operators, such as F_R and F_SP, that satisfy immediate relaxations of (SP), and in the case of F_SP, even (SP) whenever possible, have been characterized semantically, many practical questions have yet to be addressed. This technical paper aims to answer one of them: How can atoms be forgotten from a program without having to calculate its exponential number of models? To this end, we introduce two concrete representatives of F_R and F_SP that forget sets of atoms by syntactical manipulation of a program’s rules. This may in many cases prevent exponential blowups and produce a forgetting result that is close to the original program.

A Unified View on Forgetting and Strong Equivalence Notions in Answer Set Programming

“…We see that the challenging part of obtaining a relativized simplification when there are atoms to remove that do not appear in the context programs brings us closer to (SP)forgetting. In order to obtain a fully syntactic operator, an interesting follow-up work would be to see whether the existing syntactic (SP)-forgetting operators (Berthold et al 2019;Berthold 2022) can be adjusted to consider (rSP).…”