Project Scheduling with Flexible Resources: Formulation and Inequalities

In this work an extension of the resource constrained project scheduling problem is studied in which the resources are flexible. This means that each resource has several skills. Each activity may require several resources for each skill. A mixed-integer linear programming formulation is proposed for the problem as well as several sets of additional inequalities. Due to the fact that some of these inequalities require a valid upper bound to the problem, a heuristic procedure is proposed. Computational experience is reported based on randomly generated data, which indicates that for instances of reasonable size, the proposed model enlarged with the additional inequalities can be solved efficiently using a commercial package.