RE: State Alignment and Standard Signals

This is how I would approach the problem.

 

I would create a construct called Protocol. A protocol is itself a
choreography, and more precisely a choreography template. This
choreography is of course performed between abstract roles (let's call
them initiating role and responding role).

 

 

Initiating                                    Responding

            --- Request --->
Abstract message

            <---- Receipt ---
(concrete) signal

            <---- Acceptance---
(concrete) signal

            <---- Response ---
Abstract message

            --- Receipt --->
(concrete) signal

            --- Acceptance--->
(concrete) signal

 

When this template is used, every abstract message must be associated to
a concrete message.

 

In addition I should be able to associate "states" to this choreography,
e.g. 

-          RequestAccepted = positive request Acceptance signal
received, 

-          ResponseAccepted = positive Response Acceptance signal
received. 

"Positive" acceptance/response represents an XPath expression on a
message.

 

In a choreography, I should be able to specify (apologies, I don't know
the syntax by heart):

 

<choreography ... >

            <interaction type="procotol">

                        <protocol ref="myProtocol">

                                    <message name="Request"
type="ProcessPO"/>

                                    <message name="Response"
type="AckPO"/>

                                    <state name="OrderProcessed"
boundTo="RequestAccepted"/>

                                    <state name="OrderAccepted"
boundTo="ResponseAccepted" conditionExpression="//PO/@accepted="true"/>

                        </protocol>

            </interaction>

            <choice>

                        <switch value="OrderAccepted">

                           <case value="true">

                                    <interaction
type="Request/Response">

                                                ... process payment ...

                                    </interaction>

                           </case>

                           <case value="false">

                                    ... choreography ends ...

                           </case>

                        </switch>

</choice>

</choregraphy>

 

 

I promised David that I will make a formal proposal, I hope within the
next couple of weeks. Is this kind of approach acceptable?

 

Jean-Jacques 

 

________________________________

From: Gary Brown [mailto:gary@enigmatec.net] 
Sent: Friday, July 16, 2004 8:25 AM
To: Jean-Jacques Dubray; david.burdett@commerceone.com;
tony.fletcher@choreology.com; public-ws-chor@w3.org
Cc: Robin.Milner@cl.cam.ac.uk; kohei@dcs.qmul.ac.uk;
yoshida@doc.ic.ac.uk
Subject: Re: State Alignment and Standard Signals

 

Hi

 

Do you have an example of how the CDL would look in order to represent
this state alignment (e.g. as you have described in your article), in
such a manner that the interactions are protocol independent? Would you
see a "state aligned" interaction only completing after the second
(acceptance) signal in the BPSS case?

 

For example, 

 

    <interaction A->B />

 

would only be deemed to have completed once B had sent the acceptance
message to A?

 

Curious to know how such a state alignment protocol could be modelled in
CDL in an abstract manner that is decoupled from a particular
binding........

 

Regards

Gary