Task Engine Framework?

[Nate]

Hello,

I'm in the process of developing a task engine / workflow module for
my Python application and I'm wondering if anyone knows of existing
code that could be used or adapted.  Since I know that's far too
generic a question, let me share my goals:
1) Support long running operations (think backing up millions of
files) where:
   - The operation can be paused (application closed) and the
operation resumed later.
   - Individual tasks can be chained, run in parallel, or looped over
(the workflow part)
2) Would like to graph each defined operation (task A starts task B
with parameters... ) for documenting algorithms in Software Design
Document
3) Each individual task in the operation would a self-contained
class.  I'd imagine implementing its action by defining a doTask()
method.

Hopefully that's clear.  I just feel like someone must have already
solved this elegantly.  I greatly enjoy Python and I look forward to
proving its use as a valuable language for a Masters student even
though everyone thinks I should use C# :-).

Thanks!
-Nate
Masters Student at Eastern Washington University