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

Re: simultaneous execution

From: Assaf Arkin <arkin@intalio.com>
Date: Thu, 31 Jul 2003 11:41:00 -0700
Message-ID: <3F2962BC.8020000@intalio.com>
To: jdart@tibco.com
CC: Burdett David <david.burdett@commerceone.com>, public-ws-chor@w3.org

Jon Dart wrote:

> This was discussed a bit at the F2F.
> IMO it is not desirable to have to add data to Web service messages in 
> order for those messages to be part of a choreography. There are 
> simple cases where you don't need to do this explicitly. E.g. if you 
> are using HTTP and the reply goes back over the same socket as the 
> request, then you have an implicit correlation across request and 
> reply. But you don't have this implicit correlation if there's an 
> exchange of multiple communications that don't share the same session. 
> Also if you're using an asynchronous protocol, then correlation will 
> have to be part of the message content, as you note.


Then there's always the possibilty to use the extended addressing 
mechanism of WS-Addressing, or the message sequencing of WS-RM.


> The proposed WS-MessageData spec from BEA might be used as a basis for 
> this kind of correlation information.
> --Jon
> Burdett, David wrote:
>> Jon
>> What you are stating as a requirement is that it should be possible 
>> to for
>> two choreographies "executed" at the same time.
>> To fully define this requirement you actually need some extra 
>> statements,
>> more specifically the requirement should be ... "It should be 
>> possible for
>> two (or more) instances of the execution of choreographies of the 
>> same type
>> to occur between the same service instances".
>> A simple example of this is a single buyer placing two (or more) orders
>> *simultaneously* with the same seller where the buyer and seller send 
>> and
>> receive using the same instances of their order placement and order 
>> receipt
>> software.
>> If you accept this requirement, it implies a further requirement 
>> which is
>> ... "A role in a choreography must be able to identify the instance of a
>> choreography to which any message in a choreography belongs".
>> I think the only practical way of meeting this requirement is by 
>> carrying in
>> the message metadata that allows the two following information items 
>> to be
>> identified:
>> 1. Choreography Type - which identifies which choreography is being 
>> followed
>> 2. Choreography Instance Id - which identifies which particular 
>> instance of
>> a choreography the message relates to. This item was called a 
>> "Conversation
>> Id" in ebXML messaging.
>> David
>> -----Original Message-----
>> From: Jon Dart [mailto:jdart@tibco.com]
>> Sent: Thursday, July 24, 2003 1:02 PM
>> To: public-ws-chor@w3.org
>> Subject: Re: Web Services Choreography Requirements 1.0 draft uploaded
>> Kudos and thanks to the editors for getting this out.
>> A few comments:
>> re: 4.3 Scalability. One of the requirements I have mentioned is 
>> re-entrancy: execution of a choreography flow should not block 
>> execution of another instance of the same flow (e.g. two orders 
>> coming in from customers should be able to be processed in parallel). 
>> (This is in the F2F minutes, I believe). This may be purely an 
>> implementation issue, but we shouldn't preclude it at the spec level, 
>> or assume serialized execution.
>> (This is different from D-CR-040 or D-CR-041 because I'm not talking 
>> about parallel flows within a choreography, but parallel execution of 
>> choreography instances).
>> D-CR-009 is a special case of D-CR-061, I think. Maybe they should be 
>> grouped together.
>> Re D-CR-049 (design-time validation): it isn't really clear to me 
>> what this means. What does "correct behavior" mean at design time? 
>> Absence of deadlock, or ?
>> The doc needs a spell check.
>> --Jon
>> Daniel_Austin@grainger.com wrote:
>>> Greetings,
>>>        The most recent draft of the requirements document has been 
>>> uploaded to the archive list (still having problems uploading to 
>>> W3C). It's here:
>>> http://lists.w3.org/Archives/Public/www-archive/2003Jul/0024.html
>>>        This version is labeled 1.0, and is dated for July 30th, next 
>>> Wednesday, for publication after our next call, based on the group's 
>>> approval.
>>>        Please review this document carefully. Much has changed since 
>>> the last version. Here's a summary:
>>> * requirements (some 60+) have been added to the document.
>>> * the use cases have been largely rewritten
>>> * references are now available (though not yet footnoted)
>>> * many other changes
>>>        I'd like to ask that the entire group carefully review this 
>>> document with a view to publication on July 30th. The document is 
>>> not entirely ready to be published, there is still some minor 
>>> publication clean up to be done. Otherwise, it's not a bad first 
>>> working draft of the group's requirements.
>>> On behalf of my fellow editors,
>>> D-
>>> *************************************************
>>> Dr. Daniel Austin
>>> Sr. Technical Architect
>>> daniel_austin@grainger.com
>>> 847 793 5044
>>> Visit http://www.grainger.com
>>> "If I get a little money, I buy books. If there is anything left 
>>> over, I buy clothing and food."
>>> -Erasmus

"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 Thursday, 31 July 2003 14:42:13 UTC

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