INTRODUCTION
The problem of allocating resources for multiple concurrent projects appears in large cases of service and manufacturing organizations. A paradigmatic example can be an engineering projects office. This organization makes different kinds of projects that are proposed at any time, which must be handled in a given time frame. Each project consists of a number of activities (calculations, design, checks, budgeting, etc.) that are performed by workers and with some precedence relationships. The workers can perform one or several activities according to their skills. Decision makers have to reject inadvisable projects and decide which resources will be allocated to which projects and when. Previous decisions have high impact in the office’s profit. In order to achieve strategic goals it is important to give priority to projects, and to allocate activities to the most efficient workers at the appropriate time. Because of this,
before executing projects it is advisable to make a schedule that optimizes the allocation of resources.