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Re: Intermediaries - various cases

From: <jones@research.att.com>
Date: Fri, 27 Sep 2002 15:07:18 -0400 (EDT)
Message-Id: <200209271907.PAA04581@bual.research.att.com>
To: UCorda@SeeBeyond.com, www-ws-arch@w3.org

I've wondered about this case as well.  Succinctly -- What
distinguishes a dynamic routing intermediary from publish-subscribe
[assume that in either case, there can be multiple recipients]?  It
does seem to depend on the logical view.  In the publish-subscribe
case, the emphasis seems more on the middleman.  In the dynamic
routing intermediary, the emphasis is on reaching the recipient's
services.  There also seems to be more of a bias that
publish-subscribe may be asynchronous, whereas the dynamic routing
intermediary is more synchronous.

--mark

Mark A. Jones
AT&T Labs
Shannon Laboratory
Room 2A-02
180 Park Ave.
Florham Park, NJ  07932-0971

email: jones@research.att.com
phone: (973) 360-8326
  fax: (973) 236-6453


	From: Ugo Corda <UCorda@SeeBeyond.com>
	To: "'www-ws-arch@w3.org'" <www-ws-arch@w3.org>
	Date: Thu, 26 Sep 2002 14:37:41 -0700
	Subject: Intermediaries - various cases

        ...

	The discussion about intermediaries near the end of today's conf call
	reminded me of a couple of cases I have been thinking about in the context
	of queuing infrastructures.

	Suppose I have a store-and-forward node to which I send SOAP messages to be
	forwarded to particular destinations. I specify the destination in an
	extension header, and I send the SOAP message to the store-and-forward node.
	The store-and-forward node receives my SOAP message and sends it to the
	final destination (possibly later, if the final destination is not available
	right away). It looks like in this case the Service Requester (according to
	our architecture diagram) is the node issuing the initial SOAP message, and
	the Service Provider is the final destination node. So the store-and-forward
	node must be the Intermediary.

	But now let's think about a case where I have a publish-and-subscribe node.
	I send a SOAP message to that node with the intent that my message be
	distributed to any subscriber (I don't even know the address of those
	subscribers). So I send my SOAP message to the publish-and-subscribe node
	(the only node I am aware of) without specifying any final destination. In
	this case, is the publish-and-subscribe node still an intermediary, and are
	the destination nodes Service Providers? Or is the publish-and-subscribe
	node the Service Provider, which engages in separate interactions with the
	subscriber nodes? Or is there no single answer to these questions, and it
	all depends on the logical view that I want to apply to the scenario?

	Ugo
Received on Friday, 27 September 2002 15:07:52 GMT

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