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Re: Issue 133: SOAP and Web Architecture: Draft sentences for HTTP bi nding preamble.

From: Paul Prescod <paul@prescod.net>
Date: Tue, 19 Feb 2002 05:19:46 -0800
Message-ID: <3C7250F2.D24E27C8@prescod.net>
To: Martin Gudgin <marting@develop.com>
CC: Paul Prescod <paulp@activestate.com>, "Williams, Stuart" <skw@hplb.hpl.hp.com>, xml-dist-app@w3.org
Martin Gudgin wrote:
> 
>...
> 
> It is unclear ( to me at least ) how such a call would differ from a
> standard HTTP GET. What would make it SOAP? 

I don't want to get into a philosophy of "what is SOAP" because that's a
whole 'nother rant. ;)

But consider this use-case: a SOAP message that is logically a getter
bridges either from MQSeries to HTTP or back. I think that the client
should issue XML-based SOAP which becomes HTTP-friendly SOAP. SOAP
headers are bridged to (admittedly lengthy) HTTP headers (or an entity
body part?). SOAP parameters are bridged to HTTP parameters.
mustUnderstand to M-GET. etc. I admit I haven't worked out all of the
details because I'm just jumping in when I noticed that Mark's issue is
being resolved while he is away. I don't have time to fix this today. ;)

> ... Just the fact that the HTTP
> response would contain an Envelope element? Or the fact that the
> Content-Type header of that response would be application/xml+soap? Or both?
> Also, given that the Envelope will *NOT* be used to serialize the request is
> it really SOAP, given that the Envelope is a core part of the spec? Given
> that the envelope is hierarchical ( it is an Infoset, after all ) I'm not
> sure I can see a reasonable way to encode it into the query string (
> although I can see how you might encode very simple requests into the URI ).

Of course hierarchy can be flattened. And the top-level is by definition
not hierarchical so it can be flattened into ElementType=value pairs.

> Also, it would seem *VERY* problematic to try and use SOAP Headers in such
> an example, where are we supposed to put those in a GET? I understand that
> idempotent HTTP requests should use GET. But it seems that some of the
> things I might want to include in an idempotent SOAP request might include
> SOAP headers. Are you suggesting we define a way to encode SOAP headers as
> HTTP headers?

Makes sense to me.

> Or maybe the query string should just be ?xml='<soap:Envelope....' in which
> case perhaps all these problems go away... Is that what you think we should
> do?

No, the distinction between headers and query is 

Mark Baker and others have spent weeks discussing the issues on the list
and it wouldn't make sense for me to try and repeat all of that:

 * http://lists.w3.org/Archives/Public/xml-dist-app/2001Aug/0203.html
 * http://lists.w3.org/Archives/Public/xml-dist-app/2002Feb/0024.html
 * http://aspn.activestate.com/ASPN/Mail/Message/XML-Dist-App/759803
 * http://lists.w3.org/Archives/Public/xml-dist-app/2002Feb/0006.html
 * http://lists.w3.org/Archives/Public/xml-dist-app/2002Jan/0444.html
 * http://lists.w3.org/Archives/Public/xml-dist-app/2002Jan/0416.html
 * http://www.ietf.org/internet-drafts/draft-baker-soap-media-reg-00.txt
 * http://lists.w3.org/Archives/Public/xml-dist-app/2002Jan/0260.html
 * http://lists.w3.org/Archives/Public/xml-dist-app/2002Jan/0029.html

From my point of view, the uniqueness of the addressable information
namespace is arguably the most important web axiom of all. It is the key
to the web's success and will be the key to the survival of any new
generic protocol deployed on the Internet. It's unfortunate but
understandable that it wasn't baked into SOAP from the beginning. Just
as an anecdote of where this popped up recently:

 * http://lists.w3.org/Archives/Public/www-tag/2002Feb/0091.html

See also:

 * http://www.w3.org/2001/tag/ilist#whenToUseGet-7

 Paul Prescod
Received on Tuesday, 19 February 2002 08:23:10 GMT

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