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Re: Conversations and choreography (was RE: Definition of Terms)

From: Assaf Arkin <arkin@intalio.com>
Date: Wed, 26 Mar 2003 11:13:50 -0800
Message-ID: <3E81FBEE.1070905@intalio.com>
To: Francis McCabe <fgm@fla.fujitsu.com>
CC: edwink@collaxa.com, "'WS Choreography (E-mail)'" <public-ws-chor@w3.org>

Francis McCabe wrote:

> Assaf:
> On Tuesday, March 25, 2003, at 03:07  PM, Assaf Arkin wrote:
>> Edwin Khodabakchian wrote:
>>> Assaf
> <snip/>
>>> It seems to me that you are introducing the term choreography and
>>> conversation to address the problem of recursive composition (or 
>>> lack of
>>> it).
>> At this level I'm only discussing composition. There's nothing 
>> recursive about it.
>> If you describe X as sending, Y as receiving, and X+Y as choreography 
>> that's a composition. If you describe conversation X, conversation Y, 
>> and interleaving of X, Y as choreography that's also a composition. 
>> At this level there is no recursion.
> A composition is not the same thing as a choreography! At least, from 
> my POV, a composite service is a service (i.e., can participate in 
> choreographies); and it has an internal structure that is `visible' in 
> some sense. 

I agree that a composite service is not the same as a choreography.

However my statement was not about a composite service, but used the 
term composition in a generic sense. So I want to clarify how I use 
composition and related terms.

Composition - To combine parts to create a whole. Does not apply to 
specific parts or whole.

Putting two operations in a sequence is a composition. Combining two 
conversations to form a larger choreography is also a composition.

Some example:

part(1): operation X
part(2): operation Y
    action perform X
    action perform Y

Recursive composition - A form of composition which where the parts and 
whole are of the same generic type.

For example, composing two choreographies to form another choreography, 
or composing two services to form a new service.

Some example:

part(1): process X
part(2): process Y
  process Z
    call X
    call Y

Service composition - A form of recursive composition where the parts 
and whole are services (or service types).

Some example:

part(1): service type X
part(2): service type Y
  service type Z
    uses X
    uses Y


> Frank

"Those who can, do; those who can't, make screenshots"

Assaf Arkin                                          arkin@intalio.com
Intalio Inc.                                           www.intalio.com
The Business Process Management Company                 (650) 577 4700

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Received on Wednesday, 26 March 2003 14:18:20 UTC

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