Quantifying over Optimum Answer Sets
This work addresses a specific modeling gap in ASP(Q) for optimization problems, which is incremental as it builds on an existing formalism.
The paper tackles the limitation of Answer Set Programming with Quantifiers (ASP(Q)) in elegantly encoding optimization problems requiring polynomial oracle calls, by extending it with weak constraints to handle both local and global optimization. The result includes showcasing modeling capabilities and studying computational properties, such as complexity results and non-obvious characteristics.
Answer Set Programming with Quantifiers (ASP(Q)) has been introduced to provide a natural extension of ASP modeling to problems in the polynomial hierarchy (PH). However, ASP(Q) lacks a method for encoding in an elegant and compact way problems requiring a polynomial number of calls to an oracle in $Σ_n^p$ (that is, problems in $Δ_{n+1}^p$). Such problems include, in particular, optimization problems. In this paper we propose an extension of ASP(Q), in which component programs may contain weak constraints. Weak constraints can be used both for expressing local optimization within quantified component programs and for modeling global optimization criteria. We showcase the modeling capabilities of the new formalism through various application scenarios. Further, we study its computational properties obtaining complexity results and unveiling non-obvious characteristics of ASP(Q) programs with weak constraints.