process instance versioning

i think jbpm could offer some degree of assistence in process instance versioning.

when a new version of a process is deployed, jbpm could do the following conversion for a process instance :

• input required: mapping of the nodes from the old to the new definition.
• cancel the old process instance
• create a new process instance and copy the runtime (exe) information such as tokens and process variables from the old process instance.
• then establish a special link between the 2 process instances to indicate that the new process instance is the continuation of the old process instance.

this way we can avoid the problematic conversion of logs, while still keeping them in the system.

NOTE: i believe that Bernd has got some code for this in jBPM 3. That could be used as a basis.