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[jwt-dev] Re: STP IM and JWT metamodel

Hi Florian,

Andrea gave you the detailed answers for your questions, so I just want to say that if you're looking for help with transformations you can definitely count on us. So if you have any questions about transforming elements from JWT to STP-IM or the other way around, feel free to fire them up on the STP mailing list, you'll get an answer quickly.

Also, to follow up on what Andrea said and what I noted previously, the STP-IM is a generic "transporter" model, intended to bridge the variety of SOA editors in STP. So, the semantics of properties to different elements can differ based on the transformation that is going to use them. The idea is that we do not try to offer all the semantics in the IM, rather just the means to attach it, so that we can keep a high level of generality while still preserving the most important SOA concepts as top-level.

Looking forward to working with you guys,
Best wishes,
Adrian.

On Dec 21, 2007, at 11:36 AM, Andrea Zoppello wrote:

Hi,

See the comments inline.

Florian Lautenbacher ha scritto:
Hi Adrian, hi Andrea,

thanks for your helpful clarification about the metamodel of STP IM. I now
had a closer look at the metamodel in your SVN and it is (in my opinion)
much better designed than the one that is shown on your web site. In fact
the core concepts are very similar to the core metamodel of JWT (which can
be found on [1]). In STP IM you got a Process which contains * Steps and *
Transitions. Each step has a name, a description, a number of
sourceTransitions and targetTransitions as well as several
observableAttributes. You also got ControlServices with subclasses like
SplitControl or JoinControl. There can be normal Transitions or
TransitionsUnderCondition. And (nearly?) everything is a configurable



element.

Now looking at the JWT metamodel it is very much alike: here everything is a
ModelElement. There are ActivityNodes which are connected via ActivityEdges
(using source, target, in and out with same cardinality as
sourceTransitions, targetTransitions etc. in STP IM). There can be several
types of ActivityNodes: one would be an Action (probably a Step in IM) or it
could be a ControlNode such as a ForkNode or a JoinNode. An ActivityEdge
might have a Guard (making it a "TransitionUnderCondition") whereas the
Guard is specified in a GuardSpecification (with only a proprietary notation
allowed).


Regarding your description of Properties and ObservableAttributes I guess
that data that is necessary for execution (which might have been added to
BPMN and shall be transformed into BPEL e.g.) is added as a property to the
relevant step, am I right?


Yes.

For example for a Step that is configured with Service [StartService] ServiceBinding [HTTP-InputBindingComponent] the
properties will be driven by the HTTP-InputBindingComponet, So the step will have properties like:


URL:
isSoap:
and so on.


Quite different is the concept of relevant data:

Relevant data are extracted when the process is executed, evluating expression on messages ( exchanged by endpoint in the case of Jbi )
or variable in the case of ( BPEL).


An example of relevant data is customerID extracted by /RECORD/ @customerId

Thanks for clarification about the owner attribute. Yes, I was more thinking
about a participant or role than about an owner. Is this data (e.g. which is
available in a swimlane or pool in BPMN) then added as a property right now
to each Step?


As i say in previous post we'e not yet provided in the stp intermediate model the concept of participiant role.
BTW i think that we could support this in BPMN editor in two ways:


1) Using the lane ( ant this will add some additional property on the step, or better it will configure a particular
RolebAssignedStep, HumanTaskStep )
2) Get a view with a participiant list that we could drag anbd drop on the activities


We cannot use the BPMN pool concept beacuse a pool in the im is mapped in to a process.

I agree with Adrian and Marc that a first step would be having a
transformation from JWT to STP IM (and the other way round). However, since
the metamodels are quite similar, this should not be so hard. Here at JWT we
need to discuss who will be responsible for this task. Maybe somebody of STP
might be able to assist us here!?


You're welcome. Ask what you want???
I am still wondering how you are planning to include the information from
one metamodel in a way that it is clear in a next transformation step where
it should go. So, if I specify the owner of a step in a pool or lane in
BPMN, how is this information kept in STP IM so I can work with that when
generating e.g. BPEL or XPDL-code? I guess you need some predefined values
as properties that both model transformations use!? Or will there be a
query language (such as RQL or SPARQL) where you can find the "semantics" of
the property?
Best regards and looking forward to some more fruitful discussions,


Florian


Intermediate Model is a very generic model so you could have situations where some properties ( for example
of the step ) will be important by code generator A and others will be need by code generator B.


The concept is that IM bring you the information in a very generic way, than is
responsibility of specific code generator to transform that information in something executable.


To bring you an example, now i'm working in generating servicemix service assembly applications from intermediate
model, and it's my codegenerator plugins that knows ( for example how to organize service units, how to make cfg files
and so on .... ).


I don't know if it's clear, if you've some doubt please write me.

Regards
Andrea
[1] http://wiki.eclipse.org/images/2/2f/AgilPro_MetamodelDescription.pdf

-----Ursprüngliche Nachricht-----
Von: Andrea Zoppello [mailto:andrea.zoppello@xxxxxx] Gesendet: Montag, 17. Dezember 2007 10:15
An: Florian Lautenbacher
Cc: Adrian Skehill; Adrian Mos
Betreff: Re: Current state of STP IM?


Hi,

Sorry for the late response but i'm just come back from Javapolis.

See comments inline
Adrian Skehill ha scritto:

Florian Lautenbacher wrote:

Hi,

I am wondering what the current state of the STP Intermediate model is? Is the version on the Wiki [1] up to date?

I think version on the wiki is not updated. The version that we're going to
commit will be the really the first version.



If so, I am curious why a step is part of a process, but the transition is not?
And, on the other hand, why there is only one edge between a step and a transition with cardinality *. In many other standards (like UML activity diagrams) there are always two edges between a node (=ActivityNode in UML) and a transition (=ActivityEdge in UML) specifying that a transition has exactly two ends (cardinality of 1 at each edge)?



In the version that we're going to commit a process will have a set of steps
and a set of transitions. A transition wil have a source step and a target
step then in the A step there will be two inverse relations a relation
called sourceTransitions 1.* ( all transition for which the step is a source
step ) and a realtion called targetTransition ( all transition for whcih the
step is target )



How are the conditions at TransitionUnderCondition specified? Are these boolean conditions connected with AND, OR, XOR and NOT? Or is this open to each implementation (BPMN, SCA, JBI, etc.)?


The transition under condition will have a "Condition" ( Condition abstract
entity ) where a condition could be an "ExpressionCondition" ( a condition
expressed in some language Xpath, groovy, or a condition on header
properties "PropertyCondition".


Do only Transitions have ObservableAttributes? How about attributes that are specified at a step?

In the actual version of the Intermediate Model we've introduced the
relation between Observable Attribute and Step ( 1..* each step could have
one or more observable attribute ).


By the way what's important is to clarify the difference between
"ObservableAttribute" and "Property" of a Step.

Properties are information needed to configure the step in a particular
runtime,and the properties set depends by ServiceBinding.
Observable attribute are data that will be extracted when the process will
be executed to be visualuzed and monitored, by monitoring tools.



Does a process or a step has no owner, but only a service?


A process is a subclass of service so process could have owner.
What's important is to make distinct the concept of "Owner" from the
concept of "Participiant/Actor/Role" as we mean when we talk about workflow
and in general process that require "human task".


At the moment we've not in the model the concept of "Particpiant/ Actor/Role"
for the support of worflow concept, but in the future we're going to
introduce something about.


Basically ( it's just an idea that we need to discuss with other members
) we'll introduce the concept of role, and a subclass of Step entity ( let
me say RoleAssignedStep or HumanTaskStep ) where we model the relation
beteween a step and a role.


For "Owner" instead we mean the provider of a service ( process ) as it is
in service registry ( UDDI ) world.
But this part is not complete yet.


Looking forward to your answers,



Feel free to contact me if you need other information.

Florian Lautenbacher
-JWT project lead-


[1] http://wiki.eclipse.org/STP_Internal_Model_Discussion

Hi Florian,


Hi Andrea Zoppello






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