Workflow using ABAP Class

Hi,

I'm creating a Workflow and want to use a ABAP Class instead of BOR. My class implements the necessary Interface IF_WORKFLOW but I'm not sure how to implement the method BI_PERSISTENT~FIND_BY_LPOR. I don't know whats the INSTID should be because the class should be a general service class for the Workflow, so I don't have a plant or material number.

Should I generate a GUID and use this as INSTID or what else?