Flexible modeling and execution of workflow activities

While today´s workflow management systems are well suited for the controlled execution of completely specified processes, support for dynamically changing processes is rather weak. However, new applications in the business domain and in non-traditional domains like the natural sciences or laboratory environments require support for flexibility like user interventions in workflow executions and dynamic modifications. Based on an activity meta model and an activity instance model, the paper discusses dynamic modifications and user interventions and shows how their implications to activity models and to concurrent and future activity instances can be described. Finally, we show how the basic concepts presented in the paper are realized in a prototypical implementation