Namespaces and URNs

Tim Bray tbray at
Wed Aug 5 08:25:20 BST 1998

At 07:32 PM 8/4/98, Peter Murray-Rust wrote:
>(A) The NS draft gives an example as
>	xmlns='urn:loc.govs:books'
>but a private correspondent tells me than URNs should be of the form

Hmm, while in fact URN's are still mostly a hypothetical animal, our
examples should exhibit correct URN syntax, which that one doesn't,
so it needs to be fixed.

>Are these equivalent? If so, there must be a central registry of synonyms

There is little chance of this happening.  Basically, the reason namespaces
exist is to allow software to recognize & process particular chunks of
markup.  Thus, if the W3C were to declare that for HTML4 as the W3C
defines it, the canonical URI is to be "[hint hint, Dan]", then I would
expect that a lot of HTML processors, such as those built in Redmond
and Mountain view, would gear their software to recognize that 
namespace and do so right now.  

Since there is no hope of a central registry of everything, basically
namespace URIs will I expect be established via a messy market-driven
mechanism whereby certain classes of software converge around certain
canonical URIs and agree that this means HTML, that means RDF, the
other means CML, and so on.  I would expect that people who promulgate
useful vocabularies ought at the same time to publish a canonical
namespace URI, and I expect that the chances of that URI being 
bought-into by other software would be a function of

(a) how useful the vocabulary is, and 
(b) how much the group publishing the URI is trusted not to abuse
    the namespace

I.e. Peter, you ought, in the near future, to publish a canonical
URI for CML.  It doesn't need to be a URN; in fact, in the near-term,
I would be nervous about using URNs since they are (relatively speaking)
poorly understood and not widely implemented [pause for obligatory
flaming from URN fans].  The W3C ought to publish some canonical
URI for HTML and for SMIL and XML and CSS and a bunch of other things.
Microsoft *did*, to their credit, publish a canonical URI for
XML-data. -Tim

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