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Choreography awareness (was RE: Correlation Requirements)

From: Martin Chapman <martin.chapman@oracle.com>
Date: Fri, 5 Sep 2003 17:02:00 -0700
To: "'Burdett, David'" <david.burdett@commerceone.com>, <jdart@tibco.com>, "'Francis McCabe'" <fgm@fla.fujitsu.com>
Cc: "'Monica Martin'" <monica.martin@sun.com>, "'Yves Lafon'" <ylafon@w3.org>, "'Ugo Corda'" <UCorda@SeeBeyond.com>, "'Cummins Fred A'" <fred.cummins@eds.com>, <public-ws-chor@w3.org>
Message-ID: <007c01c3740a$1a690110$6401a8c0@us.oracle.com>

I think it’s a bit na´ve to think that an existing web service can somehow
be plugged into a 
choreography and magically conform to the choreography rules. However I
believe that
it should be possible to use standard wsdl with no special choreo extensions
or 
interfaces. Is this what you mean Frank?

Martin.

> -----Original Message-----
> From: Burdett, David [mailto:david.burdett@commerceone.com] 
> Sent: Friday, September 05, 2003 2:58 PM
> To: 'jdart@tibco.com'; Francis McCabe
> Cc: Burdett, David; 'Monica Martin'; 'Martin Chapman'; 'Yves 
> Lafon'; 'Ugo Corda'; 'Cummins Fred A'; public-ws-chor@w3.org
> Subject: RE: Correlation Requirements
> 
> 
> >>>There may even be a set of services that you want to 
> coordinate in a
> particular fashion to achieve a particular goal (e.g., the 
> warehouse, credit card, delivery services combine to deliver 
> a book.)<<<
> 
> In this case aren't you just defining a business process over 
> which you have total control where you are just using the 
> existing services within their already pre-defiined constraints?
> 
> If this is true you don't need a CDL and the services you use 
> don't need to be changed to become choreography aware - i.e. I agree.
> 
> But that's not the problem I am thinking of.
> 
> Let's suppose a seller has a service that can accept orders. 
> When the service receives the order it needs to know how to 
> respond, and, also know what types of messages the buyer 
> might send next. As I said in my earlier email we have 
> identified 14 different ways of placing an order.
> 
> As I see it, there two ways you *could* solve this problem:
> 1. Define 14 different services where each one corresponds to 
> a different way of doing business, or 2. Define 1 service 
> that is choreography aware where each message sent identifies 
> in some way the choreography that is being followed.
> 
> I prefer the second approach for solving *this* problem as it 
> is easier to manage and easier to re-use existing services in 
> new and novel choreographies as you don't need new service 
> definitions ... at least that is the way I see it.
> 
> I am not actually disagreeing with anything you're saying. I 
> just think that there are basically two types of problems 
> here: 1. Where a single entity (e.g. a business) is designing 
> a process that is using existing services in their standard 
> ways in this case a CDL or choreography aware services is not 
> needed 2. Where two or more entities need to use one or more 
> of their existing services in various different ways and they 
> need to know which variation to follow - this is where a CDL 
> and a way of identifiying it in a message is useful.
> 
> David
> 
> -----Original Message-----
> From: Jon Dart [mailto:jdart@tibco.com]
> Sent: Friday, September 05, 2003 1:29 PM
> To: Francis McCabe
> Cc: Burdett, David; 'Monica Martin'; 'Martin Chapman'; 'Yves 
> Lafon'; 'Ugo Corda'; 'Cummins Fred A'; public-ws-chor@w3.org
> Subject: Re: Correlation Requirements
> 
> 
> 
> +1.
> 
> The description of particular service requirements and 
> capabilities is 
> generally in WSDL, or in WS-Policy, which can be viewed as a 
> supplement 
> to WSDL, not at the choreography layer. The set of such 
> requirements and 
> capabilities is expanding all the time.
> 
> BPEL hasn't placed correlation-related requirements on 
> services, either, 
> but has provided a mechanism through which business processes can 
> specify what the correlation mechanism is, in a flexible way that is 
> conformable with multiple emerging specs in this area.
> 
> --Jon
> 
> Francis McCabe wrote:
> > A given service will have its *way* of doing things. That 
> may, or may 
> > not
> be, fully described in a choreography document. There may 
> even be a set of services that you want to coordinate in a 
> particular fashion to achieve a particular goal (e.g., the 
> warehouse, credit card, delivery services combine to deliver 
> a book.) Each of these (say) does its thing in a rich way, and
> *I* want to document how to use them to achieve the book 
> delivery service - I should be able to do that in a CDL 
> without impacting any of the existing services. A corollary 
> of that is that there may be no way of determining what 
> choreography a given message is part of (by looking at the 
> messages), it is simply an interpretation of the CDL. 
> 
> 
> 
> 
Received on Friday, 5 September 2003 20:01:42 GMT

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