Re: State Alignment and Standard Signals

Gary Brown wrote:

> Hi David
>  
> As Monica pointed out in a previous email, " we are implementing the 
> technical interactions, as the
> business aspects are outside of WS-CDL".

mm1: If you look at JJ's and Anders' comments, it discusses there is 
more than one level of state alignment. The receipt of a message is one 
such level.  I agree legal status of a message is a business level 
concern. I am not certain that the message exchange achieves 'real state 
alignment', however. 

> I would suggest that the legal status of a message 
> (signal/acknowledgement) is a business level consideration. For 
> example, if participant A sends a request to participant B, and the 
> CDL defines a sequence that indicates that a response is then sent 
> from B to A following the receipt of this request, then that implies 
> participant B has received and processed the message.
>  
> <sequence>
>     <interaction A->B />
>     <interaction B->A />
> </sequence>
>  
> As Participant B has sent a follow-up communication that could only 
> have resulted as a consequence of receiving the request, it would not 
> be able to argue that it hadn't received the request. 

mm1:  Yet, at the business level, the argument does occur. And a comment 
on your previous point, inference (i.e. implication) is often insufficient.

> I am not sure what value defining a specific message type would add. 

mm1: Perhaps the answer lies in the inference you allude to Gary, that 
the message types can provide further clarity as to the impact/relevance 
of the messages exchanged. Thanks.

>   ----- Original Message -----
>
>     *From:* david.burdett@commerceone.com
>     <mailto:david.burdett@commerceone.com>
>     *To:* tony.fletcher@choreology.com
>     <mailto:tony.fletcher@choreology.com> ; public-ws-chor@w3.org
>     <mailto:public-ws-chor@w3.org>
>     *Cc:* Robin.Milner@cl.cam.ac.uk <mailto:Robin.Milner@cl.cam.ac.uk>
>     ; kohei@dcs.qmul.ac.uk <mailto:kohei@dcs.qmul.ac.uk> ;
>     yoshida@doc.ic.ac.uk <mailto:yoshida@doc.ic.ac.uk>
>     *Sent:* Thursday, July 15, 2004 1:24 AM
>     *Subject:* State Alignment and Standard Signals
>
>     Tony
>      
>     I thought it might be worthwhile putting on record the comment I
>     made on the call on Tuesday in that I think that there are two
>     different "state alignment" problems to be solved: "real" state
>     alignment, and standard signals.
>      
>     REAL STATE ALIGNMENT
>     The first is the problem you discuss below that there is a general
>     requirement at various points in a choreography that each
>     participant has a common shared understanding of the state of the
>     other participants in terms of the messages that have (or have
>     not) been received ... I hope I am paraphrasing/simplifying your
>     requirement as described below.
>      
>     STANDARD SIGNALS
>     The second is the problem that Anders Tell described in his email
>     [1] that I responded to in my email [2]. Anders talks about a need
>     that a recipient of a message "legally" accepts that he has
>     received the message. In this case, the message is more like a
>     signal that informs the sender of the original message what their
>     "state" is with respect to legal acceptance of the message. There
>     are also other signal messages that can occur, for example to
>     indicate that a message has been received, i.e. a simple Ack, or
>     has been "Accepted for Processing" as standards like BPSS suggest.
>      
>     SOLVING THE PROBLEMS
>     To solve the problem you are suggesting, then we need to continue
>     discussing the state alignment approaches you describe below.
>      
>     To solve Anders problem and also the issues I think Jean-Jacques
>     was raising, we could define some "standard" Message Content Types
>     that have specific semantics, message flow patterns and behaviors
>     associated with them and then recommend use of these standard
>     types when choreography designers have a need to use them. Note
>     that these would specify the types and not the representation of
>     those messages in XML which could potentially be done in different
>     ways.
>      
>     Thoughts?
>      
>     David
>      
>     [1]
>     http://lists.w3.org/Archives/Public/public-ws-chor/2004Jul/0009.html
>     [2]
>     http://lists.w3.org/Archives/Public/public-ws-chor/2004Jul/0012.html
>

Received on Thursday, 15 July 2004 09:59:48 UTC