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RE: A REST challenge

From: David Orchard <dorchard@bea.com>
Date: Tue, 16 Jul 2002 15:37:22 -0700
To: "'Paul Prescod'" <paul@prescod.net>, "'Francis McCabe'" <fgm@fla.fujitsu.com>, <www-ws-arch@w3.org>
Cc: "'Mark Baker'" <distobj@acm.org>
Message-ID: <007a01c22d19$5acd9510$0100007f@beasys.com>

Paul asked a question about how one would do correlation in SOAP...  Well -
aside from a small tech problem with 3 versions being retrieved :-( - we've
got something at http://ftpna2.bea.com/pub/downloads/SOAPConversation1_0.htm

We can talk about implementation experience rather than theory.

There's a very important debate going on here, specifically about the
utility of URIs as a data format, versus the use of XML.

In the SOAP Conversation spec, XML is used to define the conversation ID
separately from the callback-URI.  So the XML extensibility model is
utilized.  You can imagine doing exciting things like adding security
information - when calling back, use this particular security token - and
others to the XML model.

If everything related to the resource identification is ALWAYS munged into
the URI, then it is harder to extend the model for new interface features.
URIs have a hierarchical notion - ie. correlation/security/some other
stuff - whereas XML allows us to have a much more expressive content model.

IMHO, the difference between wanting to use XML's capabilities for
expressing information versus the URI data model is perhaps the core of the
debate.  The REST folks believe that you have to use URIs and HTTP (AND ONLY
URIs and HTTP) for everything necessary to access the resource, and others
think that XML is a fine extensible format for encoding information about
resource access, and it even works over other protocols.  To try to come up
with a "folksy" summary.  Again, I argue that XML breaks the whole issue of
resource access and identification wide open.


> -----Original Message-----
> From: www-ws-arch-request@w3.org [mailto:www-ws-arch-request@w3.org]On
> Behalf Of Paul Prescod
> Sent: Tuesday, July 16, 2002 1:11 PM
> To: Francis McCabe; www-ws-arch@w3.org
> Cc: Mark Baker
> Subject: Re: A REST challenge
> Francis McCabe wrote:
> >
> >...
> >
> > Think a little about it. You are building a single system that is
> > simultaneously maintaining a server presence and acting as
> a user agent.
> > The two facets need to be coordinated; if you want the left
> hand to know
> > what the right hand is doing.
> Let's be concrete.
> POST /call-back/server/
> callback-URI: http://www.myhomeaddress.com/myuri/CORRELATIONID_1234
> Now the call-back server calls back
> host: www.myhomeaddress.com
> Note that the user agent can embed *as much* information in
> this URI as
> it needs to recognize the appropriate callback. In fact, however, the
> original POST could have also supplied all sorts of correlating
> information in the body.
> How would you do this otherwise with SOAP?
> > This was the motivation in suggesting that an identity was
> necessary in
> > maintaining a permanent presence in P2P style interactions.
> Even if you were right that identity was important (which in
> some cases
> it is, and some it isn't), identity can be established easily.
> POST /call-back/server/
> callback-URI: http://www.myhomeaddress.com/myuri/CORRELATIONID_1234
> <message>
> <peer_identity>http:///some_uri_representing_my_identity</peer
> _identity>
> You'll notice a trend. URIs and hyperlinks are a core part of REST.
> That's why Mark and others have a terminological mismatch
> when they say:
> "Web Services are not just about hypermedia." In Mark (and my) view of
> the world a purchase order is hypermedia because it has references to
> customer resources, supplier resources, product resources, etc.
> --
> Come discuss XML and REST web services at:
>   Open Source Conference: July 22-26, 2002, conferences.oreillynet.com
>   Extreme Markup: Aug 4-9, 2002,  www.extrememarkup.com/extreme/
Received on Tuesday, 16 July 2002 18:38:53 UTC

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