When you must forget: Beyond strong persistence when forgetting in answer set programming*. Issue 5 (30th August 2017)

• Record Type: Journal Article
• Authors: GONÇALVES, RICARDO; KNORR, MATTHIAS; LEITE, JOÃO; WOLTRAN, STEFAN
• Editors: Rocha, Ricardo; Cao Son, Tran
• Is Part Of: Theory and practice of logic programming. Volume 17:Issue 5/6(2017)
• Page Start: 837
• Page End: 854
• Publication Date: 2017-08-30
• Subjects: forgetting, -- Answer Set Programming, -- strong equivalence, -- relativized equivalence, -- computational complexity; Logic programming -- Periodicals; Artificial intelligence -- Computer programs -- Periodicals; Constraint programming (Computer science) -- Periodicals; 005.115
• DOI: 10.1017/S1471068417000382
• Languages: English
• ISSNs: 1471-0684

Abstract

Abstract: Among the myriad of desirable properties discussed in the context of forgetting in Answer Set Programming, strong persistence naturally captures its essence. Recently, it has been shown that it is not always possible to forget a set of atoms from a program while obeying this property, and a precise criterion regarding what can be forgotten has been presented, accompanied by a class of forgetting operators that return the correct result when forgetting is possible. However, it is an open question what to do when we have to forget a set of atoms, but cannot without violating this property. In this paper, we address this issue and investigate three natural alternatives to forget when forgetting without violating strong persistence is not possible, which turn out to correspond to the different possible relaxations of the characterization of strong persistence. Additionally, we discuss their preferable usage, shed light on the relation between forgetting and notions of relativized equivalence established earlier in the context of Answer Set Programming, and present a detailed study on their computational complexity.