CALL FOR PAPERS Constraints Journal Special Issue on Symmetry in Constraint Programming GUEST EDITORS Ian Gent, University of St Andrews, U.K. Jean-Francois Puget, ILOG, France. Barbara Smith, Cork Constraint Computation Centre, Ireland. INTRODUCTION Many constraint satisfaction problems have some symmetry: any assignment can be transformed into a set of symmetrically equivalent assignments. The symmetries preserve solutions, so that if any assignment in a symmetry equivalent class is consistent with the constraints, they all are. For instance, in many CSPs some of the variables refer to entities that are indistinguishable, and the values assigned to these variables can be interchanged in any solution. Where symmetry exists in a CSP, dealing with it effectively is often critical to the success of solving the CSP. Unless this is done, search often thrashes, revisiting symmetrically equivalent states over and over again. CSP solving techniques have also been used to solve symmetry-related problems. For instance, they have been used to answer the question of whether a particular search state is symmetrically equivalent to one already explored. Constraint programming techniques have the potential to improve on existing algorithms for solving similar group-theoretic problems. Symmetry in constraint programming has been an active area of research for several years, and much significant work has not yet appeared in journals. To rectify this, papers are solicited for a special issue of the Constraints Journal. Papers on any aspect of symmetry in constraint programming are welcome, including: * symmetry detection * exploitation of symmetry e.g. heuristics which use symmetry information * elimination or avoidance of symmetry e.g. by remodelling the problem, adding constraints, or modifying the search algorithm * exploitation of mathematical techniques such as group theory * applications of constraint programming to problems with symmetry. PAPER SUBMISSION Researchers are invited to submit original papers that make a significant contribution to the field to constraints-symmetry@dcs.st-and.ac.uk. (Note that the usual on-line submission procedure for the Constraints journal will not be followed initially for the Special Issue). All submissions should be in .pdf format and follow Constraints Journal guidelines. Papers are expected to be about 20-25 journal pages. When submitting, please use the subject "Constraints Special Issue Paper Submission" and clearly specify the e-mail address and phone number of the corresponding author. Receipt of papers will be acknowledged. Submissions will be reviewed by at least two reviewers. All accepted papers will meet the usual high-quality standards of the Constraints Journal. Intending authors should send an expression of interest (including a provisional title, list of authors and a few sentences outlining the topic of the paper) to constraints-symmetry@dcs.st-and.ac.uk by the end of June, 2006. IMPORTANT DATES Expression of interest: end of June, 2006 Submission of papers: end of September, 2006 Notification of acceptance: end of December, 2006 Final versions of accepted papers: end of February, 2007 Expected publication of the Special Issue: mid-2007 Special issue homepage: http://www.dcs.st-and.ac.uk/~ipg/symmetry Constraints Journal homepage: http://ai.uwaterloo.ca/~vanbeek/Constraints/constraints.html