Experimenting with Namespaces - DTDs?

David Megginson ak117 at freenet.carleton.ca
Tue Mar 31 23:27:51 BST 1998

Chris Smith writes:

 > But also as a developer, this seems to make this almost impossible to
 > even experiment with namespaces. As far as I can tell, DTDs are what
 > give you the ability to eXtend XML - without a comparable tool
 > involving namespaces, I can't specify what the eXtension is. The notes
 > suggest that changes to Namespaces are unlikely (not impossible,
 > just...). But changes to XML 1.0 also appear to be unlikely in the
 > near future. The only option available seems to be to ignore
 > Namespaces, since I can't find a way to use them that will give me any
 > benefits that XML hasn't already given me - unless I start to abandon
 > XML 1.0 in favour of a non-existent-non-standard XML 1.1 that has a
 > namespace aware DTD notation.

There is another (somewhat unattractive) option: you can use your own
schema notation internally, then export it as an XML 1.0 DTD for

As Jon Bosak explained in his announcement, the namespace spec was
brought out very quickly because other efforts like RDF had a
dependency on it -- ideally, it would have waited six months or a year
until there was time to deal with schemas, etc., but that wasn't

Personally, I'd recommend architectural forms over namespaces if
you're concerned with DTDs, since architectural forms have several
major advantages:

1. they work very well with XML 1.0 DTD syntax
2. they allow multiple inheritance
3. they allow you to hide the namespaces from the author (unless the
   author cares to poke around in #FIXED attribute values)
4. they are allowed to be declared in the external DTD subset
5. they are a more mature technology
6. they are part of an International Standard

Namespaces may or may not become more useful in the future, depending
on what the XML WG decides about schemas -- for now, they make a very
awkward fit with XML 1.0 DTDs (they work, but as you say, they don't
give you much).

All the best,


David Megginson                 ak117 at freenet.carleton.ca
Microstar Software Ltd.         dmeggins at microstar.com

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