Another look at namespaces

David Megginson david at
Fri Sep 17 03:49:41 BST 1999

Paul Prescod writes:

 > David Megginson wrote:
 > > 
 > > 1. An application must be able to determine the general language used
 > >    by (part of) a document.
 > > 2. An application must be able to determine the specific dialect used
 > >    by (part of) a document.
 > David, can you please define "general language" and "dialect" in a
 > manner that I can implement in a computer program? 

A language is an arbitrary point in a continuum, discovered
empirically.  For example, consider the following:

  Marked-up text => SGML => HTML => HTML 4.0 => HTML 4.0 strict

There is a very large set of software that can work with HTML (more or 
less interoperably), but considerably less software that works with
SGML in general, and almost nothing that works exclusively with HTML
4.0, much less HTML 4.0 strict.  More importantly, there is a
well-defined set of behaviours associated with the software that works 
with HTML, and that set of behaviours is generally considered useful
in itself.

The same thing applies in natural languages:

  Indo-European => Germanic => English => Canadian => Ontario => Toronto

It's easy but wasteful to make too much of small distinctions, though
it's still important to be able to present them.

 > Is "XML" a general language? Is "XHTML" a dialect? Is "XSLT" a
 > language and "XSLT used with XSL FOs" a dialect? Please don't
 > appeal to my common sense or intuition because I have neither and
 > unfortunately neither does my Pentium 233.

It depends on your perspective.  Since we're talking about Namespaces
in XML documents, then XML itself is the universe, so you can remove
it from the equation.  XSLT and XSL FOs are separate languages that
happen to work well together because they don't really compete (unlike
two natural languages, and more like, say, Algebra and English).

Of course, we won't know this for certain until there are enough
implementations of XSLT and XSL FOs to see how people are using them
-- the proof is in the implementation, not the design.

All the best,


David Megginson                 david at

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