Thanks Mauricio - that's useful but my question probably wasn't clear enough.
What I'm trying to do is access the currently logged-in user Id, without having to ask that user to enter it via a form every time they start a task. I was hoping I could add a script task to my process and from that use a method call of some kind (e.g .via kcontext) to access an Id field or similar. I guess that's what you're suggesting I could do using the ProcessInstanceLog link, but for various reasons I'm constrained to use the 5.4.0.Final tooling so I'm not sure I can exploit the Console NG developments.
Where possible I'm trying to develop and deploy entirely from Drools-Guvnor and jbpm-console.
It may be that I fall into a particular class of jBPM user who is more heavily biased to the BPMN-side of things and I'll confess that I don't have a background in enterprise apps, so I'm climbing several steep learning curves every day! I'm heavily reliant on Drools-Guvnor for building and deployment my stuff with some modest Java API calls contained within Script tasks.
I can imagine that other users in my class would find it useful if the jbpm-console could automatically create, on start-up, a process global (e.g. processStartInfo?) with some key fields similar to the ones you've linked to (e.g. initiator id, date/time etc). Do you think this is this a sufficiently common requirement that it would be worth me submitting a Jira request?
Thanks again for getting back,
Andy McC