This paper comes back to the problem of coordination of cooperative activities with a Workflow management system. First, we describe the differences that we have noted between business processes and cooperative processes. Then we present a set of requirements for a Workflow management system that aims to support cooperative workflow, and among these requirements are high flexibility and dynamicity. Then we describe how this has been taken into account in the development of the Bonita workflow management system that proposes to remove the idea of process model to work only with process instances that can be derived from each others or that can be composed.