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Re: Protocol Bindings

From: Marc Hadley <marc.hadley@sun.com>
Date: Thu, 05 Jul 2001 11:09:15 +0100
Message-ID: <3B443CCB.1C65B6FF@sun.com>
To: Mark Nottingham <mnot@mnot.net>
CC: Henrik Frystyk Nielsen <henrikn@microsoft.com>, "Williams, Stuart" <skw@hplb.hpl.hp.com>, xml-dist-app@w3.org
I think we are confusing two quite different things here. For a while
now I've been uncomfortable with the notion that "everything is a
binding" such that e.g. SOAP with attachments (MIME) is treated the same
way as HTTP. IMO we have two separate concepts:

(i) Packaging Format
In this category I would put MIME (SOAPwA), DIME, ...

(ii) Transport.
In this category I would put HTTP, SMTP, BEEP, TCP, ...

The key difference I think is that transports provide for actual message
movement and hence require discusssion of things like endpoint address
format, message exchange pattern, connection/channel management, ...
Packaging formats are completely agnostic in all of these areas

In many case we will want to combine things from both categories and in
this case the following rules seem to apply:

(a) Packaging formats can be nested in any given message exchange. e.g.
one could put SOAP in MIME in DIME.
(b) 1 (and only 1) transport can be used in any given message exchange.
i.e. it makes no sense to nest one transport in another. I'm ignoring
protocol tunneling here since this is transparent to transport clients.
(c) If we are thinking in terms of nesting then the transport must be
the "outer" layer.

I think that mixing up packaging and transport under the single
umberalla of "binding" only makes things more complex for us. There are
real substantial differences between packaging and transport and we
should recognise and make use of them.

Comments ?


Marc Hadley <marc.hadley@sun.com>
Tel: +44 1252 423740
Int: x23740
Received on Thursday, 5 July 2001 06:09:35 UTC

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