W3C home > Mailing lists > Public > xml-dist-app@w3.org > November 2000

RE: DR8xx

From: Henrik Frystyk Nielsen <frystyk@microsoft.com>
Date: Mon, 13 Nov 2000 18:53:41 -0800
Message-ID: <00f101c04de6$1b5f2150$fb4c1fac@redmond.corp.microsoft.com>
To: "Lucas Gonze" <lucas@worldos.com>, <xml-dist-app@w3.org>

> Whether the recipient of a message is an intermediary may not 
> be knowable in
> advance.  It is reasonable for an intermediary to make an 
> active decision
> whether to process or forward a message.  An active proxy, 
> one which may contain
> CGI scripts, is one example.  A CGI script that optionally 
> may decide to forward
> a request elsewhere is another example.  Because there are 
> instances of both of
> these in use, this appears to be the kind of extensibility 
> actually seen on the
> Web.

Note that in HTTP terminology (which I presume you are hinting at based
on the mentioning of CGI scripts), the examples that you point out are
in fact gateways and not proxies.
> Maintaining separate codebases for active proxies and 
> forwarding servers has
> tradeoffs.  For the many P2P designs using symetrical message 
> formats, there
> would not be a simple transform between their protocols and 
> product of this WG.

There is nothing in XP intermediaries that prevents you from sending
symmetrical messages in either direction. One of the requirements of XP
is that it can support multiple message exchange patterns including
one-way messages, request/response and what have you. If you look at
current SOAP/1.1, there is nothing that prevents you from doing exactly
> I suggest that the targeting clause be amended to require that message
> components targeted at intermediaries be orthogonal to 
> message components
> targeted at endpoints.  A time to live header is an example.  
> It always affects
> nodes acting as intermediaries, and never affects nodes 
> acting as endpoints.

Nope, again I assume you refer to HTTP and in this case the
Cache-Control header field which is an end-to-end header field intended
for all caches in the message path including one (if any) in the user
agent.  We have to make clear the distinction between operations
typically performed by intermediaries and how to address them. XP has
near nothing to say about the former but a fair amount to say about the
latter. This is exactly the same as XP has near nothing to say about
what features an endpoint - only how a message should be processed.
> I am not a member of the WG, so I hope that this input is appropriate.


Received on Monday, 13 November 2000 21:54:20 UTC

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