Re: Choreography: Narrowing Down the Requirements

Hi Jeff.

* Jeff Mischkinsky <[email protected]> [2002-10-31 02:34-0800]
>   In response to the WSCG's request that we narrow down the requirements 
> before presenting our recommendation to the AC, I'd like to float a trial 
> balloon. The proposal would be to insert into the previous draft of the 
> proposed charter the text specified below (or something real close to it). 
> In addition, along the lines of our previous discussions and votes, I'd 
> suggest restricting the input documents to the one's we agreed were most 
> essential. I'll post a complete draft charter before the (Halloween) 
> telecon.
> 
> The choreography specification(s) shall define (at a minimum) the behavior 
> and language constructs for the following key concepts:
> 
>     * Composition features
[..]
>     * Associations
[..]
>     * Message exchanges
[..]
>     * Activities
>           o Message exchange interactions between web services (e.g. 
>           receive,
>             invoke, etc.).
>           o Behavior definitions (e.g. sequencing , looping, concurrent
>             execution, etc.).
>           o Assignment semantics.
>           o Relationships between activities.
>           o Scoping Rules.
>           o Nesting Rules.

Rereading your proposal, the last part seems a little fuzzy to me,
because the questions that come to mind are:
- what is an activity?
- how does it differ from a Web service, from a choreographed Web
  service?
- what assignment are we talking about?

These are all questions that a Working Group would ask itself while
developing its requirements document.

It seems to me like a means to express a flexible description. I think
that this is what Oisin was getting to also.

I would move (most of) those points under "Composition features":

     * Composition features
          + The ability to define a choregraphy as a web service, i.e. a
            recursive composition model.
          + Definition of the choreography's externally observable
            behavior.
          + Ability to represent stateful choreographies.
          + Definition of the identity of a choreography instance.
          + Lifecycle management (e.g. creation, termination, etc.)
          + Message exchange interactions between Web services (e.g.
            receive, invoke, etc.).
          + Behavior definitions (e.g. sequencing , looping, concurrent
            execution, etc.).

I believe that the rest is covered in other points (e.g.
"Relationships between activities" should be covered by
"Associations").

Regards,

Hugo

-- 
Hugo Haas - W3C
mailto:[email protected] - http://www.w3.org/People/Hugo/