Abstract: A workflow management method and system including a process definition tool enabling a user to model a workflow process definition. A workflow management engine is configured to interpret the workflow process definition to perform workflow management tasks. The definition tool and workflow management engine are configured to support primitives including an inhibitor primitive that enables modeling processes having mutually exclusive interdependencies, an option primitive that may be instantiated zero or more times, a group assignment primitive that supports group activity, and an activity placeholder that enables the specification of activities whose concrete types may be unknown at process definition time.