Re: Web Service Composition [Was RE: Revised: Mission Statement]

Assaf Arkin wrote:

>
> Reading each of the e-mails exchanged so far, I have to say they all 
> make sense. But the thread doesn't make sense at all. And following 
> the conf call discussion was downright impossible.
>
> The problem is, someone starts discussing compositions of 
> choreographies for the purpose of reuse, in response we branch into a 
> discussion about composition of services to form a new service, then 
> half-way switch to discussing composition of interfaces to form a 
> choreography, then into discussion of the choreography behind a 
> service. Lots of context switching going on, with not a single 
> participant ever saying "BTW I've just switched context form 
> discussing X to discussing Y".
>
> Perhaps we should start by identifying the different types of 
> compositions, and even if there is overlap (and I bet there is), 
> discuss each type of composition in detail as if no other type of 
> composition ever existed. Once we have some better understanding of 
> each type of composition on its own, we can throw them all in a big 
> bowl and make soup out of it ;-)

mm1: That's why I provided the original working definitions that had 
been identified in our work to try to hone in on what were our 
priorities.  See attached.

>
> arkin
>

Subject:
[ws-chor] 6/24/2003: Definitions for Composition and Semantics
From:
"Monica J. Martin" <monica.martin@sun.com>
Date:
Tue, 24 Jun 2003 14:59:38 -0600
To:
member-ws-chor <member-ws-chor@w3.org>, Jim Hendler <hendler@cs.umd.edu>

As we discussed today, here are the current working draft definitions for various types of composition. We don't have one for service semantics, although we have a reference that a failure may happen at the business level due to semantics.  Let's start the conversation.....

*Choreography Composition*: Creation of a choreography from parts that may be used to create a variety of choreographies (or a choreography of choreographies).  A choreography definition is composable if it is possible to reuse portion in the choreography definition or another one.

Note:  A choreography itself is a composition but it may not be recursive, it may be the composition of elements of other types (e.g. interfaces, services, message types, etc). A choreography may be a series of parts or more primitive.

Creation of a unit or product from components or parts.  These components or parts may be used to compose a variety of units or products (services).  Composition can imply the ability to construct complex artifacts from simpler parts.
*General Composition*: Creation of a unit or product from components or parts.  These components or parts may be used to compose a variety of units or products (services).  Composition can imply the ability to construct complex artifacts from simpler parts.

Note: A process definition can be a hierarchical composition or a process can include many processes or a recursive composition. Implies the ability to incorporate definitions by reference rather than by copy.

Clarify: Determine if service composition is associated with tasks on the client side and relate this potentially to choreography and, if accepted, orchestration.

*Interface Composition*: Is a composition of interfaces/service types that are linked to each other. These interfaces/service types can be decomposed and then recompose them into other choreographies (reuse).

*Recursive Composition*: Creation of a composition that includes more than one business process.  A recursive service composition is a composition of services that results in a new service. Can be the combination of distinct parts to form a whole of the same generic type.  A recursive choreography composition is the ability to take multiple choreographies and compose them into a larger choreography.

*Web Services Composition*: Is the combination of distinct Web service (type) to form new Web service (type).  Web services can be composed to achieve a specific goal.