[Zope3-dev] WORKFLOW: Notes on WFMC and XPDL

[Jim Fulton]

Ulrich Eck wrote:
> Hi Jim,
> 
> it seems you spent many hours studying the WfMC Docs ;-)

Yup.

> i think your restrictions make sense for a initial implementation effort
> - the remaining features can be added later when we have some experience
> with doing activity-based workflow in z3.
> 
> Am Montag, den 29.11.2004, 14:31 -0500 schrieb Jim Fulton:
> 
>>A key issue is how to interface process definitions with the rest of
>>the system.  Process definitions integrate with the rest of the system
>>through application and participant definitions. Applications appear
>>to be like functions, with input and output arguments, however, there
>>is an important difference.  Application invocation and return are
>>asynchronous. An application instance is created and usually can't be
>>executed immediately (for example if there is a human performer).
> 
> 
> afaik there is no way to invoke functions/methods asynchronous in z3 at
> this time. how do you plan to do so and how would user-interaction then
> happen - all of z3-interaction is based on a single request that ends up
> in a web-page/result?

That's why I noted that these are not like function calls.  When an application
is invoked, we'll actually create a work item.  Typcally, the factory will
place the work item in someone's work list.  Later, when the work item
is completed, typically through user interactions, the work item will make a
call on the activity to notify the activity that the work item is completed,
providing output values.

An important point here is that the process (instance, definition, whatever)
isn't responsible for aving the work items.  That is up to the application.

The key here is that applications *are* called asychronously, and, therefore,
the calls are not simply function or method calls.  It is the responsibility
of the application factory to somehow arrange that the activity gets called back
later.

Jim

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