Constraint Programming and Graph Algorithms

In the spring of ’99 my colleague Gert Smolka gave me a short introduction to constraint programming. During our discussion Gert emphasized that the search for efficient propagation algorithms leads to hard and well motivated questions in algorithmics. He pointed me to the papers [Reg94] by J.-C. Regin on “A filtering algorithm for constraints of difference in CSPs” and [GC97,GC00] by N. B. Guernalec and A. Colmerauer on “Narrowing a 2n-block of sortings in O(n log n)”. I soon learned that Gert had pointed me to an extremely rich source of algorithmic problems which I am now exploring in cooperation with E. Althaus and S. Thiel from my research group, D. Duchier and J. Niehren from the programming systems lab, A. Koller from the computer linguistics department at the Universität des Saarlandes, and with Nicolas Beldiceanu at SICS. Some papers [MT00,ADK+00,KMN00] and implementations of propagators for the Oz system (http://www.ps.uni-sb.de/oz2/) have come out of the cooperation so far. The purpose of this talk is to get more researchers from the algorithms community interested in the subject. I want to make the case that constraint programming offers a lot of very challenging algorithmic problems and that cooperations between the constraint programming and the algorithms community could be very beneficial to both communities.