A timed colored Petri nets approach to process scheduling

An algorithm is introduced for solving multiprocess scheduling problems, based on an extension of Petri nets (PNs) able to cope both with multiple processes and with time constraints. These nets are called timed colored PNs (TCPNs). The class of problems faced by the approach can be characterized as follows: there is a set of concurrent processes, each formed by a number of temporally related tasks (segments). Tasks are executable by alternate resource sets different both in performance and costs. Processes and tasks are characterized by release times, due dates, and deadlines. Time constraints are also present in the availability of each resource in resource sets. It has been proved that the problem does not admit an algorithm for an optimal solution in polynomial time. The proposed algorithm finds a suboptimal schedule according to a set of optimization criteria, based on the tasks´ and processes´ times (earliness, tardiness) and/or on the time-independent resources´ costs