W3C home > Mailing lists > Public > public-ws-chor@w3.org > July 2003

Re: "Message" semantics and composition -- WAS Grounding Choreographies (the atoms)

From: Assaf Arkin <arkin@intalio.com>
Date: Mon, 21 Jul 2003 12:57:36 -0700
Message-ID: <3F1C45B0.50107@intalio.com>
To: Andrew Berry <andyb@whyanbeel.net>
CC: Francis McCabe <fgm@fla.fujitsu.com>, public-ws-chor@w3.org

Andrew Berry wrote:

> This approach has many advantages.  In particular, when speaking of a 
> set of autonomous participants in a choreography, the behaviour of 
> each participant will be based entirely on what they are able to 
> observe from their locality.  This protects their interests and 
> ensures their autonomy.  The choreography should respect their 
> autonomy and explicitly specify the behaviour of participants based on 
> what they are able to observe locally.  The causal relationships 
> defined by the choreography then specify the expectations of other 
> participants resulting from local behaviour of a participant.


> Explicitly separating the local behaviour from causal relationships 
> also has considerable advantages for composition.  Consider Arkin's 
> example in 
> http://lists.w3.org/Archives/Public/public-ws-chor/2003Jul/0134.html: 
> we want to re-use the "message" interaction in many choreographies.  
> If a message is specified from a senders perspective as a send 
> followed by an acknowledgement, we can use this sender behaviour in a 
> number of different scenarios, including a simple message, a delegated 
> message or even a multicast message (e.g. for high availability).  If 
> we "bind" the sender's message semantics to a particular interaction 
> model then we significantly reduce the possible compositions of this 
> behaviour.

I am less in agreement on this point. While I perfectly understand the 
premise and agree with it from one specific perspective, it is not clear 
why there would be a constrast since causality can both occur inside a 
locality, and can depend on things that may be true regardless of 
autonomy or locality.

For example, if we know that a service receives X and replies with Y, as 
a requestor of that service, without violating my autonomy and 
regardless of my location, if I send X I expect to receive Y. I am fully 
autonomous in every respect, and my locality can change, but that 
causality is something I expect to happen, hence define an interaction 
around it.


> Ciao,
> AndyB
>> 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

This message is intended only for the use of the Addressee and
may contain information that is PRIVILEGED and CONFIDENTIAL.
If you are not the intended recipient, dissemination of this
communication is prohibited. If you have received this communication
in error, please erase all copies of the message and its attachments
and notify us immediately.
Received on Monday, 21 July 2003 15:59:00 UTC

This archive was generated by hypermail 2.3.1 : Tuesday, 6 January 2015 21:01:00 UTC