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RE: DR600: Transport Neutrality

From: Williams, Stuart <skw@hplb.hpl.hp.com>
Date: Tue, 14 Nov 2000 18:15:21 -0000
Message-ID: <5E13A1874524D411A876006008CD059F191F7F@0-mail-1.hpl.hp.com>
To: "'ohurley@iona.com'" <ohurley@iona.com>, "Williams, Stuart" <skw@hplb.hpl.hp.com>, xml-dist-app@w3.org
Hi Oisin

[Comments/question at the bottom only] 

> [deletia]
> > For straighforward unidirectional XP message delivery this 
> requirement is
> > fine. However, for matching 'synchonous' request/response pairs I
> > think this
> > requirement implies either:
> >
> > a) the existence of a transport independent mechanism
> > 'addressing' responses
> > and for matching request response pairs (ie. one that works say
> > over SMTP as
> > a transport as well as HTTP).
> 
> Yes.
> 
> > b) a transport specific mechanism for 'addressing' 
> responses and matching
> > request/response pairs that gets pushed downward into the 
> definition of a
> > transport binding for a given 'transport protocol'.
> 
> No.
> 
> > I think that if neither of these holds then we loose the 
> neutrality this
> > requirement is intended to "ensure".
> >
> > Have I missed something?
> 
> The implication for the coverage of RPC-style messaging is 
> that there is
> information within the message model (possibly in terms of a mandatory
> header)
> which contains some device to perform request/response 
> correlation. If the
> transport protocol in use happens to have such an artifact as 
> part of its
> makeup, then the XP mapping to that transport protocol is 
> free to use it
> as the expression of its correlation device. It is also quite 
> free to refuse
> to make use of the built in correlator and explicitly deposit 
> correlation
> data on the wire. The important thing is, whatever it does for that
> particular
> protocol should be consistent!
> 
>  cheers
>    --oh

So let's see if i've got this right...

A mechanism that relied solely on the semantics of the HTTP POST operation
would be ruled out by this requirement because, at least within the scope of
using XP for RPC that mandates a "...dependency on specific feature or
mechanism provided by a particular transport protocol beyond...".

Would that be a correct judgement based on this requirement?

Stuart
Received on Tuesday, 14 November 2000 13:15:52 GMT

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