Re: How namespace names might be used

> Why can't content negotiation handle this? The CONNEG working group    
> is looking at being able to express just such relationships...

Moving from the current situation where the namespace name is "just a
name", an identifying mark, to one in which the expected behaviour
is that the namespace name be deferenced as a URI would be a massively
retrograde step in the direction of proprietary data formats and thus
a move against the core reason for using XML at all.

An example might help, Postscript files that meet certain extra
criteria start off

%!PS-Adobe-3.0

This identifies them as postscript, and is generally a useful thing.
It also gives credit where credit is due, and acknowledges that Adobe
specified the format. However anybody can implement a postscript
compatible engine to process the file. postscript, despite being
owned as a language by one company, is an essentially open format.

If we ignore SVG for now, then an xmlisation of this
would look something like 

<PS xmlns="http://www.adobe.com/dsc/3.0">

Under XML namespaces as currently specified this has essentially the
same status as the DSC comment on the original. It is a unique
identifying mark, and credits Adobe with specifying the language.

Under your proposals the expected behaviour would appear to be that
in order to process the file you had to connect (or have connected in
the past, to use a cache) to Adobe's server.
This would be a bad thing.

And its not just postcript. Microsoft (to take a random example)
are quite capable of specifying good and useful languages for all sorts
activities. If I want to use one of those languages then I have no
objection to using whatever namespace name the author of the language
specifies. But in order to use that language, mappings between that
namespace name and the required tool configurations are going to
have to be set up. This happens by looking up the namespace name
in some configuration file (or as briefly discussed this morning) by
some global lookup. It will not happen by content negotiation at
microsofts server unless they suddenly start advertising linux
software. Saying that the way to discover facts about a namespace
is via content negotiation implies that one organisation has
control over all aspects of the namespace. This is an absolutely
bad idea.

Tim Bray, Rick Jelliffe and others have made similar arguments on this
list.

> the URI identifies the semantic resource not
> a particular representation of it.

But the resource identified by the namespace name is usually not the
namespace so this doesn't really help in this situation. This has to
be the case as long as every URI (or as now, every URI reference)
may be used as a namespace name.

David

Received on Sunday, 11 June 2000 05:21:11 UTC