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                         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@cs.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@cs.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