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RE: Proposed text on reliability in the web services architecture

From: Assaf Arkin <arkin@intalio.com>
Date: Tue, 21 Jan 2003 18:32:06 -0800
To: "Miles Sabin" <miles@milessabin.com>, <www-ws-arch@w3.org>
Message-ID: <IGEJLEPAJBPHKACOOKHNIEDJDBAA.arkin@intalio.com>


> Assaf Arkin wrote,
> > Miles Sabin wrote,
> > > Well, ultimately RM is only interesting insofar as it supports
> > > overall reliable operation.
> >
> > But who defines and exposes that operation in your example?
>
> I don't think there's a clear cut answer to that question. Suppose we
> have two "legacy" endpoints communicating via WS adapters. The
> endpoints don't know anything about WS (that's why they're legacy
> rather than services in their own right) so they can't define or expose
> anything in any sense which is relevant to the WS arch doc (ie. they
> aren't responsible for exposing WSDL, or SOAP messaging or WS RM or
> whatever). That can only be done by the WS adapters. But equally the
> adapters don't know everything of relevance to the application (that's
> why they're adapters rather than applications in their own right).
>
> So there's a gap between the parties which are making the visible
> commitments (the WS adapters) and the parties which are ultimately
> responsible for meeting them (the endpoints). Whether that gap is
> narrow and/or easily bridged, or an all consuming abyss is likely to
> vary on a case-by-case basis. I'm sure many of us on this list have
> experienced both.

You have to decide what is the service and what is the application. If you
have a message handler there that allows your application to receive
messages over HTTP, the message handler is not the service. It's a proxy
that takes care of the HTTP/SOAP/etc details on behalf of the actual
service.

A proxy does not represent his/her own opinion. The proxy must represent the
opinion of the application it represents (the actual service).

The fact that the proxy has received the entire message in its buffer
represents the opinion of the proxy, not of the opinion of the application.
As far as the application is concerned it has not received the message to
assure delivery. It's premature for the proxy to decide what the application
has to say in the matter and communicate it.

Unless the proxy and application are in agreement. So in my example the
proxy persists the incoming message and the proxy agrees with the
application that this is "as good as it gets" and so presents this opinion.
In your example the opinion is not known until the message hits the
application, so the proxy should wait until that point in time before
communicating anything.

Does that make any sense?

arkin


>
> Cheers,
>
>
> Miles
Received on Tuesday, 21 January 2003 21:33:22 GMT

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