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Re: Gateways

From: Mark Baker <distobj@acm.org>
Date: Tue, 8 Oct 2002 12:49:06 -0400
To: Ugo Corda <UCorda@SeeBeyond.com>
Cc: www-ws-arch@w3.org
Message-ID: <20021008124906.P28061@www.markbaker.ca>

On Tue, Oct 08, 2002 at 09:10:45AM -0700, Ugo Corda wrote:
> Mark,
> Very interesting. Thank you for following up on this.


> The only concern I have is that gateway is a term used in many contexts and
> at many levels on the network stack (e.g., in [1] IBM talks about a Web
> Services Gateway). So I am not completely sure what Henrik was referring to
> when he said "The first question is of course what a gateway is but if we
> strictly look at it from a SOAP node perspective ....".

I think he means that the term is used is many contexts, but we only
need to look at the SOAP context, which I agree with.

But FWIW, IMO, at all layers in the stack that I know the term to be
used, I'd say that a gateway is an element that terminates messages with
the intent of "presenting" (maybe sending, or maybe making available for
retrieval) some as-close-to-semantically-equivalent-as-possible (due
to lossy interface matching) message on the outbound interface.

So an HTTP-to-SMTP gateway would be responsible for matching up HTTP
methods and SMTP methods as close as it could, presumably allowing
inbound HTTP POSTs to go out as SMTP DATA requests (with lots of header
futzing).  But as an example of "lossy interface matching", since HTTP
is more general than SMTP, HTTP PUT messages would have no equivalent
SMTP message because SMTP cannot explicitly set the state of the
mailbox to which it's sending messages.

Mark Baker, CTO, Idokorro Mobile (formerly Planetfred)
Ottawa, Ontario, CANADA.               distobj@acm.org
http://www.markbaker.ca        http://www.idokorro.com
Received on Tuesday, 8 October 2002 12:48:06 UTC

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