WfMOpen

Basically, the group is the Id as specified in the process definition. While this Is is unique in the process definition, it is not in the process instance, because the transition may be defined in an activity block and therefore instantiated more than once. In this case the Id is augmented with informations from the activity.

Define a process with ActivityBlock and have a look at the group names generated. The group attribute is intended for advanced visualization, you shouldn't use it for anything else.

- Michael