Hi,
If you are seeing my pic attached above.
_WF_INITIATOR = This is the most used standard default container element.Useing this varibale we can find who initiated the application(Like example who created Purcahse order ,sales order).Technically speaking he is the person initiated the event.
Here you go finally found perfect link for you... I seen and Read this some days before.....
Regards,
Ragav