Abstract
Answer-Set Programming (ASP) is a declarative programming paradigm. In this paper we discuss two related restrictions and present a novel modeling technique to overcome them: (1) Meta-reasoning about the collection of answer sets of a program is in general only possible by external postprocessing, but not within the program. This prohibits the direct continuation of reasoning based on the answer to the query over a (sub)program’s answer sets. (2) The saturation programming technique exploits the minimality criterion for answer sets of a disjunctive ASP program to solve co-\(\mathsf {NP}\)-hard problems, which typically involve checking if a property holds for all objects in a certain domain. However, the technique is advanced and not easily applicable by average ASP users; moreover, the use of default-negation within saturation encodings is limited.
In this paper, we present an approach which allows for brave and cautious query answering over normal subprograms within a disjunctive program in order to address restriction (1). The query answer is represented by a dedicated atom within each answer set of the overall program, which paves the way also for a more intuitive alternative to saturation encodings and allows also using default-negation within such encodings, which addresses restriction (2).
This research has been supported by the Austrian Science Fund (FWF) project P27730.
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Notes
- 1.
On the non-ground level, this might be simulated using conditional literals as supported by some reasoners, cf. [9] and below.
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Redl, C. (2017). Answer Set Programs with Queries over Subprograms. In: Balduccini, M., Janhunen, T. (eds) Logic Programming and Nonmonotonic Reasoning. LPNMR 2017. Lecture Notes in Computer Science(), vol 10377. Springer, Cham. https://doi.org/10.1007/978-3-319-61660-5_15
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