Description and Representation of the Problems selected for the First International Constraint Satisfaction Solver Competition Fr´ ed´ eric Boussemart, Fred Hemery, and Christophe Lecoutre CRIL-CNRS FRE 2499, Universit´ e d’Artois Lens, France {boussemart, hemery, lecoutre}@cril.univ-artois.fr Abstract. In this paper, we present the problems that have been se- lected for the first international competition of CSP solvers. First, we introduce a succinct description of each problem and then, we present the two formats that have been used to represent the CSP instances. 1 Introduction For the first international competition of CSP solvers which was held as part of the CPAI’2005 workshop (http://cpai.ucc.ie/05/CPAI.html), it has been decided to only deal with constraint networks involving finite domains and con- straints defined in extension. It means that each domain corresponds to a finite set of values, and that each constraint is explicitly defined using a list of allowed or unallowed tuples. In order to avoid any ambiguity, we briefly introduce constraint networks. A constraint network consists of a finite set of variables such that each variable X has an associated domain dom(X) denoting the set of values allowed for X, and a finite set of constraints such that each constraint C has an associated relation rel(C) denoting the set of tuples allowed for the variables vars(C) involved in C. A solution to a constraint network is an assignment of values to all the variables such that all the constraints are satisfied. A constraint network is said to be satisfiable if it admits at least a solution. The Constraint Satisfaction Problem (CSP), whose task is to determine whether or not a given constraint network is satisfiable, is NP-complete. A constraint network is also called CSP instance. In this paper, we first describe the pool of problems adopted for the compe- tition and then we introduce the formats that have been proposed to represent them. We have to mention the participation of Radoslaw Szymanek, Marc van Dongen and Rick Wallace who kindly provide us with the description of some problems. Also, note that the two formats described in this paper are the results of fruitful discussions by all members of the organizing committee.