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Re: [xmlProfiles-29] xml subsetting in IETF XMPP

From: Robin Berjon <robin.berjon@expway.fr>
Date: Wed, 02 Apr 2003 10:46:44 +0200
Message-ID: <3E8AA374.7030109@expway.fr>
To: Tim Bray <tbray@textuality.com>
Cc: www-tag@w3.org

Tim Bray wrote:
> Noah Mendelsohn/Cambridge/IBM wrote:
>> (I still prefer the term "usage convention" to "subset"
> 
> I don't.  Let's call a spade a spade.  SOAP/XMLPP have created an 
> incompatible subset of XML such that general-purpose XML generators 
> cannot reliably be used to generate their messages, and general-purpose 
> XML procedssors cannot reliably be used to receive them.  It looks like 
> a subset, walks like a subset, quacks like a subset.

Imho it only looks, walks, and quacks like a subset if sending some of the 
excluded tokens generates an error, ie if general-purpose XML has a chance of 
blowing up when it reaches the other side.

On the other hand if it is defined so that the receiving end MUST parse the XML 
correctly, but MUST ignore it (ie MUST NOT pass it on to the application so that 
no semantic value whatsoever can ever be attached to those tokens) then we have 
a usage convention. It reads general-purpose XML, it just doesn't extract the 
same information out of it. Given that we have no data model, a parser that 
exposes less data than another is not a subset parser.

It is my understanding that this is the approach taken by the XMPP folks. I'm 
not saying it's devoid of potential problems (notably wrt entity handling) but 
those seem to be technicalities.

-- 
Robin Berjon <robin.berjon@expway.fr>
Research Engineer, Expway        http://expway.fr/
7FC0 6F5F D864 EFB8 08CE  8E74 58E6 D5DB 4889 2488
Received on Wednesday, 2 April 2003 03:48:55 GMT

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