The paper introduces ad-hoc workflow, adding flexibility to traditional workflow. A problem that stems from the added flexibility is the need to support end-users in the selection and modification of the process for a specific case. We propose a class of Petri nets to describe workflow processes, featuring safeness and guaranteed termination. A set of transformation rules with sufficient power for this class is given, that can be implemented in a graphical editor. A second problem is monitoring the work being done. The solution here is to approximate the states of the cases being treated by the states of a few standard cases.