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Semantic width and the fixed-parameter tractability of constraint satisfaction problems

Abstract:
Constraint satisfaction problems (CSPs) are an important formal framework for the uniform treatment of various prominent AI tasks, e.g., coloring or scheduling problems. Solving CSPs is, in general, known to be NP-complete and fixed-parameter intractable when parameterized by their constraint scopes. We give a characterization of those classes of CSPs for which the problem becomes fixed-parameter tractable. Our characterization significantly increases the utility of the CSP framework by making it possible to decide the fixed-parameter tractability of problems via their CSP formulations. We further extend our characterization to the evaluation of unions of conjunctive queries, a fundamental problem in databases. Furthermore, we provide some new insight on the frontier of PTIME solvability of CSPs. In particular, we observe that bounded fractional hypertree width is more general than bounded hypertree width only for classes that exhibit a certain type of exponential growth. The presented work resolves a long-standing open problem and yields powerful new tools for complexity research in AI and database theory.
Publication status:
Published
Peer review status:
Peer reviewed

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Publisher copy:
10.24963/ijcai.2020/239

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Institution:
University of Oxford
Division:
MPLS
Department:
Computer Science
Role:
Author


Publisher:
International Joint Conferences on Artificial Intelligence Organization
Host title:
Proceedings of the Twenty-Ninth International Joint Conference on Artificial Intelligence
Pages:
1726-1733
Publication date:
2020-07-17
Acceptance date:
2020-04-20
Event title:
29th International Joint Conference on Artificial Intelligence and the 17th Pacific Rim International Conference on Artificial Intelligence (IJCAI-PRICAI 2020)
Event location:
Yokohama, Japan
Event website:
https://www.ijcai20.org/
Event start date:
2020-07-11
Event end date:
2020-07-17
DOI:
EISBN:
9780999241165

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