A system for improved scheduling of resources within a Workflow-Management-System or a computer system with comparable functionality (WFMS). Based on a new resource specification comprised within a process model and associated with an activity, the WFMS determines the resources required for execution of said activity. The invention further schedules a request for allocation of said resources on behalf and in advance of starting execution of said activity. This approach reduces the execution time of the activity as all resources required by the activity will be available when execution of the activity begins; the activity does not have to wait for these resources. Moreover, a WFMS knowing the required resources of the activities it is administrating is able to schedule resource requests to avoid resource conflicts between the activities.