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Re: AW: [jwt-dev] Extending the JWT Editor with Extension Points?

Hi Ralph, all

Yeah, I forgot to say that we should, stay as simple as possible ^^

My first concern is to have as nice as possible XML in workflow files : it'd pain me to have XML in CDATA below Actions element...

Since we're using EMF to produce this XML, I'm having a deep look at this technology, though other are neither out of the question nor incompatible, ex. see what I said in my previous mail about XSD).

Now more about your mail :
* 1. "the other reason why I would not view extensions in the graphical editor, is that the model will become more and more unclear. We tried this a lot" -> thanks for the feedback. I agree that graphical representation of extensions is not a priority but rather a pitfall. OK for the idea of UI pages, like PropertyView. * 2. having "multiple files", ex. a core worfklow file and a "log" extension file : managing consistency of multiple files (ex. having a LogAction specify where it hooks up in the core file) may prove hard (not only for displaying it, but also for transforming it to executable processes...). I'd prefer extended information to appear where it applies, for the sake of simplicity also. So I'm not fond of this (though two files would be better than a single one with CDATAs !). * But I agree with all other ideas, especially the behaviour of the extension point. Even using EMF as model extension technology, we could provide helpers so the extension plugin writer can have access at a model object's extension information as EMF or XML (simple matter of EMF fragment <-> XML conversion) or why not even Java generated from EMF genmodel.

& you do not confuse me ^^


Ralph Soika/IMIXS a écrit :
Hi Marc,

thanks for your informations. I agree with you that the integration of schema extensions can become really hard. I have no idea how this can be done with EMF / dynamic EMF .

I want to point out two things which could make it easier.
1.) no graphical representation in the JWT Editor of extensions!
- it could be very hard to analyze the objects of an extension and view them in the graphical representation of the model. - the other reason why I would not view extensions in the graphical editor, is that the model will become more and more unclear. We tried this a lot of times at Imixs. And in the end the model was no more useful. I think the main goal of the graphical editor is to give a user a fast way to navigate throw the process. Not to show any aspect of technical details of a model. These technical details should be viewed by PropertyPages. So this is the reason why I would not expect a graphical representation of extensions and I would not advise to do so. So the vendor how wants to extend the model should not expect that the jwt-editor shows a lot of gaudy pictures. But the vendor which is extending the model by a Eclipse-Plugin should implement a PropertyView which is able to view all necessary informations of this extension. Maybe he can add an additional graphical editor which is representing the model including extensions of the vendor. But the main model from JWT Editor should still be clear and easy to understand.

2.) why not to store model informations in multiple files?!
I don't think that it isn't "eclipse like" to store complex model informations in multiple files. So if I use different extensions (Plugins) in my JWT Modeler the modeler can store this in multiple files. The filename (eclipse file resource) can be created by the JWT Main Modeler Plugin. So a vendor have to use this pre-gernerated file resource object. So the control of the files is by the JWT Mail Plugin. The content of the file is controlled by the vendor of an extension. Mybe the vendor have to write the data generated by his propertypages and also read them out if a model object was selected in the graphical JWT editor

So the behavior of the extension point could be very easy from the view of the JWT Editor:

   * The graphical Editor will not be changed.
   * The JWT Editor informs each Plugin if an Object was selected form
     the editor. So it can load the extended data.
   * The JWT Editor suports a pre-generated file resource object to the
     plugin according to the main model file to give the plugin the
     chance to store the data.
   * The Extension defines how the property page can be extended (we
     have implemented this in the Imixs IX Modeler)

If you don't like the idea with multiple files than the Extension Point can be claim a plugin to get the xml representation of the data to a specific part of the model.

So I hope that I did not confuse you all to much now?

best regards

Marc Dutoo schrieb:

Ralph, Florian, it seems things have been moving forward on your side, that's great.

Ralph, your idea of using Eclipse plugins to extend the JWT workflow metamodel is a good one and very "eclipse-like", I like it ! (See next mail)

Florian, I was thinking about that :

1. Dynamic EMF

Thank to your tipping me with the "dynamic emf" keyword, I found the following : . * "particularly interesting in scenarios where part of the application model code is generated through the EMF code generator, and the rest of the model code is built using Dynamic EMF" :) * basically, it uses EMF through its reflection API, and not databound generated classes. This (I think) makes it not ideal for extending the JWT graph editor, though it is perfect to store and retrieve typed extensions (properties...) in a unified manner. * NB. I believe the type extension can be loaded from an EMF XSD and therefore doesn't require to be coded in java.

So it would be possible
* on one side for JWT developers to do "full", development-heavy extensions that extend the core metamodel and require code generation, * and on the other side to extend JWT in a costless manner ex. by creating domain-specific tasks using only an EMF XSD describing the typed extensions (we could even provide simple samples) and a property page UI.

2. The hard part of dynamic EMF : knowing the extension XSDs

In the XML version of an EMF model, type extensions are written down as XSD schemaLocation. So the hardest part (besides actually using the extended model through the slightly cumbersome - compared to databound classes - EMF reflection API) is to provide a nice enough way to find and manage them. Here are a few ideas : * by default, trying to find the type using the schemaLocation XML header, as an absolute path or relative to the same directory as the workflow XML (or if schemaLocation is not enough, maybe define a workflow property ?) * else in a well defined "extensionRepository" directory of this JWT installation * that's another subject, but, what about defining another workflow file type : a zip file containing one workflow process file and extension type files ?

More in next mail


Florian Lautenbacher a écrit :
Hi Ralph,

yes, we had a very lively discussion on Thursday about the different aspects of workflow models and workflow engines. Thanks again for the warm welcome, Ralph! I agree with you that we should include a mechanism for any vendor to include their specific information in the workflow model. This could be the hooks of Bonita in XPDL, the JEE server data, etc. Probably that's also one
of the things Bryan and Marc are discussing in another thread. So the
generic properties we are currently implementing could be a first step.

What you suggest "use Eclipse extension points to extend the model" reminds me of a presentation I heard at this year's EclipseCon, where the concept of "Dynamic EMF" was described (I believe in the context of a tool named Skyway Perspectives). I'm not familiar with that right now and will have to read
some more, but maybe anybody else reading this mail knows about this

Anyway I'm looking more into the way the IX Workflow API and Modeler work in
order to get a better understanding how we could bring both together.

Best regards,


-----Ursprüngliche Nachricht-----
Von: jwt-dev-bounces@xxxxxxxxxxx [mailto:jwt-dev-bounces@xxxxxxxxxxx] Im
Auftrag von Ralph Soika
Gesendet: 18 April 2008 11:27
An: Java Workflow Toolbox
Betreff: [jwt-dev] Extending the JWT Editor with Extension Points?


I want to make a suggestion of how to extend the JWT Modeler with vendor
specific extensions.
We talk yesterday to Florian Lautenbacher and Bernhard Bauer and discuss the
possibility that we from Imixs use the JWT Editor in future to model
Workflow Models for our "Imixs IX JEE Workflow Engine".
The general requirement for us is that we need to model a lot of individual Informations/Attributes to each Activity inside the model. For example our engine supports a "IX Mail Module" which needs informations to generate a email during a transition. So now what I want to suggest is: Why not to use the concept of Eclipse
extension points to extend the JWT Model itself?
My idea is that a vendor should not only be able to use a predefined
extension point inside the JWT Editor to add additional property pages to an
activity object. But also a vendor can describe an individual model
extensions using the same mechanism as used by eclipse to extend a plugin.
So for example, if we form Imixs like to extend the JWT Editor with an
additional property tab to describe the informations for our "IX Mail
Module" we also add an XSD File to describe the structure of the data. The XSD File can be very similar to the XSD Files generated with the Eclipse Plugin IDE. In fact JWT can use the existing Eclipse XSD Editor concept for
In the end the JWT Editor extends the model xml file itself with the
additional structure for an activity as described in this XSD File or
creates an additional separate Model File. The informations are provided by a property page from vendor specific plugin. Later on the IX Workflow Engine
can parse the JWT Model file for specific extensions like the "IX Mail
Another aspect of this concept is hat a user of the JWT Editor can switch on and off the extensions during modeling. So I can see and model using the Imixs extensions and in the next moment I switch off this extension and can see the natural model. Than I can switch on a extension from another vendor to see other aspects of the same model. This could be also a way to implement real round-trip-modelling.

What did you think about this?

best regards

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