Hi,
As HuiSheng Xu ask me, I send you my point of view about that subject...
AFAIK, there are serveral needs linked to put user information in a process.
- find some process by userid (by adding userid in process instance info),
- enforce the usage of identity, user who start the process could be the default assignee (with a particular EL for exemple),
- Check if the user could start an instance of a particular process (need some adds in jpdl to descripe that !)
Regards