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Re: INT: Intermediary Discussion

From: Hugo Haas <hugo@w3.org>
Date: Thu, 1 Feb 2001 15:25:19 -0500
To: XML Protocol Comments <xml-dist-app@w3.org>
Message-ID: <20010201152519.C5420@tux.w3.org>
On Thu, Feb 01, 2001, Martin Gudgin wrote:
> The glossary[1] currently defines the following term
> XP intermediary
> An application that can act as both an XP sender and an XP receiver with the
> purpose of forwarding an XP message along an XP message path.

I think that we should make it clearer that an XML Protocol
intermediary is not the ultimate destination of the message. "can"
implies that it could only be an XP receiver, and the ultimate XML
Protocol receiver would qualify as an intermediary, and I don't think
that it should.

> Various people have commented that intermediaries come in various forms.
> 1.    Intermediaries in the TCP stack. For example standard IP routers.
> 2.    Intermediaries in the HTTP stack. For example an HTTP caching proxy.

Those are what the requirements document (section 4.4.1) calls
transport intermediaries. The December face-to-face minutes[2]

   DECISION: Diagram as edited at the meeting is accepted.  "Underlying
   protocol" is the term adopted.
   Fallside: Issue of how we relate underlying protocols to the use of
   the term "transport" intermediaries

Underlying (protocol) intermediaries sounds weird... I liked transport
intermediaries, and to paraphrase server 4.4.1:

  A transport intermediary is an intermediary which operates at the
  underlying protocol level. It cannot be addressed from within an XML
  Protocol envelope.

> 3.    Intermediaries in the XP 'stack'. For example ??????

For example an XML Protocol application which would stick some
authentication information in a message being sent to another site.

  An XML Protocol intermediary is an application which processes a
  defined set of blocks in an XML Protocol message along an XML
  Protocol message path. It acts both as an XML Protocol receiver and
  an XML Protocol sender in order to forward the XML Protocol message
  towards the ultimate XML Protocol destination.

> 4.    Intermediaries in the 'B2B stack'. For example a brokerage that acts
> as a go between for purchasers and vendors.

What about application-level intermediary, i.e. an intermediary
operating at a higher level, on top of XML Protocol?

> [1] http://www.w3.org/TR/xp-reqs/#N3030
  2. http://www.w3.org/2000/xp/Group/0/12/f2f-minutes

Hugo Haas - W3C/MIT
mailto:hugo@w3.org - http://www.w3.org/People/Hugo/ - tel:+1-617-452-2092
Received on Thursday, 1 February 2001 15:25:19 UTC

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