An improved multi-mode resource allocation and project scheduling model

In this paper we extend the Petri net based scheduling model that was previously introduced (2007). The integer programming (IP) model of the scheduling problem stated previously may yield an optimal solution that is not an implementable (feasible) schedule. In this situation other alternate optimal solutions of the IP model, if any, must be generated and checked whether they are feasible schedules. The process of generating alternate optimal solutions can be very time consuming or computationally impractical. In this paper, we provide a modified IP model that its optimal solution is always an implementable schedule. With this modification, there is no need to generate alternate optimal solutions. This modification significantly reduces the time required to produce an implementable schedule.