Computing weighted solutions in ASP: representationbased method vs. searchbased method
 Duygu Cakmak,
 Esra Erdem,
 Halit Erdogan
 … show all 3 hide
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For some problems with too many solutions, one way to obtain the more desirable solutions is to assign each solution a weight that characterizes its importance quantitatively, and then compute the solutions whose weights are over (resp. below) a given threshold. This paper studies computing weighted solutions for a given computational problem, in the context of Answer Set Programming (ASP). In particular, we investigate two sorts of methods for computing weighted solutions: one method suggests modifying the ASP representation of the problem to compute weighted solutions using an existing ASP solver and the other suggests modifying the search algorithm of the answer set solver to compute weighted solutions incrementally. The applicability of these methods are shown on two sorts of problems: reconstructing weighted phylogenies (for IndoEuropean languages and for Quercus species) and finding weighted plans (for Blocks World planning problems). In the experiments with the representationbased method, the answer set solver clasp is used and weight functions are represented in ASP. For the searchbased method, the algorithm of clasp is modified (the modified solver is called claspw) and weight functions are implemented in C+ +. For phylogenies, two weight functions are introduced by incorporating domainspecific information about groupings of species; one of them cannot be represented in ASP due to some mathematical functions not supported by the ASP solvers. For plans, we define a weight function that characterizes the total cost of executing actions in a plan. In these experiments the following are observed. With weight measures that can be represented in ASP, the searchbased method outperforms the representationbased method in terms of computational efficiency (both time and space). With weight functions that cannot be represented in ASP, the searchbased method provides a tool for computing weighted solutions in ASP. The searchbased method can be applied to different domains, without modifying the algorithm of claspw; in that sense, the searchbased method is modular and can be useful to other ASP applications. With either method, plausible phylogenies among many can be found without computing all phylogenies and requiring historical linguists to go over them manually, and less costly plans can be found without computing all plans; in that sense, our methods contribute to phylogenetics and AI planning studies as well.
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 Title
 Computing weighted solutions in ASP: representationbased method vs. searchbased method
 Journal

Annals of Mathematics and Artificial Intelligence
Volume 62, Issue 34 , pp 219258
 Cover Date
 20110701
 DOI
 10.1007/s1047201192421
 Print ISSN
 10122443
 Online ISSN
 15737470
 Publisher
 Springer Netherlands
 Additional Links
 Topics
 Keywords

 Weighted solutions
 Answer set programming
 Weighted phylogenies
 Weighted plans
 92B10
 92D15
 68T20
 68T27
 68T30
 68N17
 Industry Sectors
 Authors

 Duygu Cakmak ^{(1)}
 Esra Erdem ^{(1)}
 Halit Erdogan ^{(1)}
 Author Affiliations

 1. Faculty of Engineering and Natural Sciences, Sabancı University, Istanbul, Turkey