Employee Timetabling, Constraint Networks and Knowledge-Based Rules: A Mixed Approach

Employee Timetabling Problems (ETP) are all around us. One possible approach for solving ETPs is to use constraint processing techniques. Another approach that has been used many times in the past is to model human knowledge into knowledge-based systems for timetabling. It is diicult to represent the complex constraints of timetabling explicitly in constraint networks. On the other hand, knowledge-based representations of constraints are implicit and cannot support any of the heuristics of constraint based processing that have been developed over the last decade. The present report presents an apptoach to representing and processing employee timetabling problems (ETP) by a combination of explicit representations of some constraints in the network and rule-based processing in which spe-ciic heuristics for generic constraints of ETPs are embedded. The mixed-mode approach described above has been implemented in the form of a commercial software package for deening and solving real world ETPs. Examples of a family of real world ETPs are followed through the presentation and are quantitatively used to experimentally compare processing by standard CSP techniques and by the proposed mixed-mode approach.