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From Andreas Hartmann <andr...@apache.org>
Subject Re: Workflow definition document
Date Tue, 03 Jun 2003 15:06:39 GMT
Hi Daniel,

Daniel Fagerstrom wrote:

> Andreas Hartmann wrote:
>> Hi Lenya developers, 
> Hi, I'm not a Lenya developer, but I have been lurking on the list for a 
> while and am very interested in having a workflow engine that can be 
> used from Cocoon. There are numerous use cases for a workflow engine in 
> that context besides publishing.

first of all - thanks for your reply and your interest!

We decided to restrict the functionality of our interfaces to the 
minimum that is needed for Lenya.

My intention was to create a very simple API and a basic implementation
that can be replaced by an adapter for an existing engine. I kept the
CMS stuff out of the workflow API for SoC reasons.

I can spend very little time on implementing a flexible or more
comprehensive solution, but I might be interested in integrating
an existing engine if this makes Lenya more stable or standards


>> --------------------
>> a) general + fexible
>> -------------------- 
> I would prefer this solution. As far as I can see, there is nothing in 
> the basic state and transition model, or the workflow interfaces in the 
> CVS that are specific for publishing. And as mentioned above there are 
> so many use cases for WF outside publishing that it IMO would be a good 
> idea to keep the WF engine rather flexible.

Actually, I also prefer this one. But my intention is not the
application outside of Lenya, but the implementation of
publication-specific conditions and actions.

If you really think that the API can be used for other purposes,
feel free to use it! But I'm afraid the current community won't
invest much work in making it more flexible than we need for Lenya.
Of course, if you want to do so - that would be great!
The more applications there will be, the more consolidated
code will develop (at least I hope so ...)

> It would also be rather easy to build such a more flexible WF engine as 
> there allready is a framework in Cocoon for building language 
> interpreters. Take a look at the package 
> org.apache.cocoon.components.treeprocessor. Sylvain Wallez wrote the 
> treeprocessor a few years ago as he wanted to have a sitemap interpreter 
> instead of a compiler. Back then there were also discussion about 
> building a XML based flow handeling language within Cocoon, so he wrote 
> a framework that was suposed to be general enough for building general 
> XML configured interpreters that are based on Avalon components.

Thanks for the info! I will take a look at the TreeProcessor.

> If you are interested in using the treeprocessor for implementing the WF 
> engine, and more generaly in "Avlonizing" the WF components I would be 
> happy to contribute.

At least the latter one would be very interesting. I already thought
about "Avalonizing" :) the engine.

> Going more into the details in your proposal I think that the main ideas 
> look good. I also think that it could be a good idea to take a close 
> look at the sitemap and try to follow the conventions from it.

 > It will
 > be much easier to learn Lenya and other Cocoon based framework
 > if there is some common style for all configuration files.

In fact, I already had this idea :)
The basic structure (declaration of components, usage of components)
is very similar. I decided against this to keep the files simple,
but maybe it's really worth a thought to make it similar to sitemaps.
Is this a general pattern that appears also in other document

Let's see what the others think.

> I also wonder about how you are integrating the WF engine with the 
> sitemaps, I looked in the mail archives and browsed the code and 
> couldn't find anything. Could you please give a link or some description 
> of it.

We probably won't integrate the WF with the sitemaps directly.
I don't know if you're familiar with the Lenya task concept,
this will be the main link between WF and CMS functionality.


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