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Consequences of SOAP GET to Web Services?

From: Mark Baker <distobj@acm.org>
Date: Fri, 14 Jun 2002 05:06:39 -0400
To: www-ws-arch@w3.org
Message-ID: <20020614050639.C23893@www.markbaker.ca>


For those of you who don't follow the TAG or the XML Protocol Working 
Group, the TAG recently said[1] that the lack of GET support in the 
default SOAP 1.2 HTTP binding was counter to Web architecture.  The
implications of this decision, and the resulting response[2] of the XML
Protocol Working Group, should, IMO, be studied carefully by all 
working groups in the Web Services Activity, and the Web Services 
Architecture Working Group in particular.

The first and most obvious thing that this means, is that if the 
underlying protocol is HTTP, that a SOAP developer must be aware of 
that fact.  In other words, it is counter to Web architecture to treat
SOAP as a layer when bound to HTTP, which virtually all SOAP 1.1 based
Web services do.

Today, for us, this means that D-AR003.1[3] is incorrect (at least what 
it's intended to mean), and should be rephrased to ensure that the Web 
services reference architecture exposes the semantics of underlying 
application protocols (or at the very least, HTTP GET).  This was also 
*roughly* the conclusion[4] of a recent discussion - with limited input
by the WG - about this draft requirement.

This decision also highlights the value of D-AR003.2[5], the recently 
added draft requirement on an "a priori interface".  "GET" is a key
method of this interface, as are the other HTTP methods that operate on 
resources, plus the "faults" (aka "status codes") that those methods 
return.  I discussed this here[6].

Going forward, I suggest that this decision has significant consequences 
for our work.  Primary amoungst them, I believe, is that the "assumed 
architecture" that many (most?) WG members have in mind - the one that
looks like OMA/CORBA - does not have very much to do with Web 
architecture, and any architectural decisions that are made assuming
that it does, will inevitably meet with objection from the TAG if we 
incorporate them into our work.

I look forward to some discussion on what other WG members thinks this
means for us.

 [1] http://lists.w3.org/Archives/Public/xmlp-comments/2002May/0018
 [2] http://lists.w3.org/Archives/Member/tag/2002Jun/0006 (member only)
 [3] http://www.w3.org/2002/ws/arch/2/06/wd-wsa-reqs-20020605.html#AR003.1
 [4] http://lists.w3.org/Archives/Public/www-ws-arch/2002May/0443
 [5] http://www.w3.org/2002/ws/arch/2/06/wd-wsa-reqs-20020605.html#AR003.6
 [6] http://lists.w3.org/Archives/Public/www-ws-arch/2002May/0302
Mark Baker, CTO, Idokorro Mobile (formerly Planetfred)
Ottawa, Ontario, CANADA.               distobj@acm.org
http://www.markbaker.ca        http://www.idokorro.com
Received on Friday, 14 June 2002 04:56:49 UTC

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