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Re: Internal processes and/or external choreographies (was RE: Ev ents and States ...

From: Assaf Arkin <arkin@intalio.com>
Date: Fri, 11 Apr 2003 10:27:51 -0700
Message-ID: <3E96FB17.7020801@intalio.com>
To: Jean-Jacques Dubray <jjd@eigner.com>
CC: steve@enigmatec.net, "'Cummins, Fred A'" <fred.cummins@eds.com>, "'Burdett, David'" <david.burdett@commerceone.com>, jdart@tibco.com, public-ws-chor@w3.org

These are the examples I have given, not a full authorative list of all 
possible examples. What I have ommitted is not excluded. A request is 
also an event.

In fact, sending a message, receiving a message, or a time instant are 
three types of events.

Sending a message is an event. Receiving a message is an event. There's 
a causal dependency - receiving message event occurs after sending 
message event (for same message). There may also be more elaborate 
causal dependencies - receiving a response following a previously sent 
request. In fact, every pattern you could come up with is expressible 
using these very simple terms.

And if you look at everything from the perspective of events and causal 
dependencies you can use other formalisms, e.g. Lamport clocks, to model 
and prove synchronization even in the most demanding of environment, 
even when you have to deal with Byzantine failures (also a Lamport concept).

The formalism accounts for multiple types of events. The primary ones 
are send, receive and with patterns you get one-way, request-response, 
etc. There are also chaostic events, which allow you to deal with 
time-outs and more general failure detection. This model is at the core 
of distributed algorithms, failure detection and mobile process calculus.

It is used to describe high-level protocols such as the Web, low-level 
protocols such as cell phones, and even the way we communicate and 
conduct business in the offline world. That's what makes it such an 
appealing model.


Jean-Jacques Dubray wrote:

>I am not sure I understand you argument about event. All the examples
>that you give for an event seem to b e responses to a request, but how
>do you model the request itself as a message event? In my opinion, it is
>really the completion of a message exchange pattern that constitutes an
Received on Friday, 11 April 2003 13:30:11 UTC

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