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Problem #43

Originator: Jean-Pierre Jouannaud
Date: April 1991

Summary: Design a framework for combining constraint solving algorithms.

Design a framework for combining constraint solving algorithms.

Remark

Some particular cases have been attacked: In [BS92] it was shown how decision procedures for solvability of unification problems can be combined. In [BS93] a similar technique is applied to (unquantified) systems of equations and disequations. In [Rin92] the combination of unification algorithms is extended to the case where alphabets share constants. In related work [Bou92], unification is performed in the combination of an equational theory and membership constraints.

Some further progress is in [Rin92].

The combination approach of [BS92] has been extended in [BS95a] to constraints involving predicate symbols other that equality, and [BS95b] in turn extends this approach to constraint-solving over solution domains that are not free structures. These results are presented in a uniform framework by [BS98].

The work of [Rin92] has been extended to the case of “shared constructors” by [DKR94].

Comment sent by Miki Hermann

Date: Mon Apr 27 12:05:20 MET DST 1998

Unification algorithms (and therefore also constraint solvers) cannot be combined in polynomial time, as proved by Hermann and Kolaitis in [HK96].

References

[Bou92]
Alexandre Boudet. Unification in order-sorted algebras with overloading. In Kapur [Kap92].
[BS92]
Franz Baader and Klaus Schulz. Unification in the union of disjoint equational theories: Combining decision procedures. In Kapur [Kap92].
[BS93]
Franz Baader and Klaus Schulz. Combination techniques and decision problems for disunification. In Claude Kirchner, editor, 5th International Conference on Rewriting Techniques and Applications, volume 690 of Lecture Notes in Computer Science, pages 301–315, Montreal, Canada, June 1993. Springer-Verlag.
[BS95a]
Franz Baader and Klaus Schulz. Combination of constraint solving techniques: An algebraic point of view. In Jieh Hsiang, editor, 6th International Conference on Rewriting Techniques and Applications, volume 914 of Lecture Notes in Computer Science, pages 352–366, Kaiserslautern, Germany, April 1995. Springer-Verlag.
[BS95b]
Franz Baader and Klaus Schulz. On the combination of symbolic constraints, solution domains, and constraint solvers. In Ugo Montanari and Francesca Rossi, editors, Principles and Practice of Constraint Programming, volume 976 of Lecture Notes in Computer Science, Cassis, France, September 1995. Springer-Verlag.
[BS98]
Franz Baader and Klaus Schulz. Combination of constraint solvers for free and quasi-free structures. Theoretical Computer Science, 1998. To appear.
[DKR94]
E. Domenjoud, F. Klay, and C. Ringeissen. Combination techniques for non-disjoint equational theories. In A. Bundy, editor, 12th International Conference on Automated Deduction, volume 814 of Lecture Notes in Computer Science, pages 267–281, Nancy, France, 1994. Springer-Verlag.
[HK96]
Miki Hermann and P. G. Kolaitis. Unification algorithms cannot be combined in polynomial time. In M. A. McRobbie and J. K. Slaney, editors, 13th International Conference on Automated Deduction, Lecture Notes in Computer Science, pages 246–260, New Brunswick, NJ, July/August 1996. Springer-Verlag. To appear in a special issue of Information and Computation.
[Kap92]
Deepak Kapur, editor. 11th International Conference on Automated Deduction, volume 607 of Lecture Notes in Computer Science, Saratoga Springs, NY, June 1992. Springer-Verlag.
[Rin92]
Christophe Ringeissen. Unification in a combination of equational theories with shared constants and its application to primal algebras. In A. Voronkov, editor, International Conference on Logic Programming and Automated Reasoning, volume 624 of Lecture Notes in Artificial Intelligence, St. Petersburg, Russia, July 1992. Springer-Verlag.

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