XML in the real world... Was "Re: Another look at namespaces"

Paul Prescod paul at prescod.net
Fri Sep 17 14:58:28 BST 1999

Tyler Baker wrote:
> In the case of most applications, they build there own data structures directly from an
> event-based XML parser or else from some sort of object-oriented framework which delegates the
> events to some sort of abstract element API. If you get an unknown form of element content,
> the application can choose how to handle it as it wishes. Whether this element content is
> supposed to be there is defined by programmer documentation which may include a DTD as a
> reference (such as in the XSLT spec). If expected element content does not occur within the
> scope of the containing element being processed, then the application can fill in the default
> values as it sees fit.

Part of the zen of SGML (inherited by XML) is that standards exist to
protect end users from programmers.

If the definitive *executable* specification for an interchange language
is a software product then the that product's vendor essentially owns
that language. So for instance there is an open specification for "RTF"
but there is no such thing as an RTF "validator" so the definitive
specification for what is or is not valid RTF is Word for Windows. End
users that want to check an RTF document's conformance do so by pumping
it through Word. This puts every competitor to Microsoft at a
disadvantage and that in turn hurts end users. HTML has the same
problem. XHTML is trying to move away from that.

On the other hand, the definitive executable specification (validator)
for Docbook is the DTD and Docbook producing software can be easily
tested for conformance using neutral (and free) third party tools. One
could imagine a world in which there were hundreds of "hand-coded"
validators for RTF, HTML (there are!), and every other language but once
you've written a few of these you come to think: "wouldn't it be better
if there was a generalized way to do that."

 Paul Prescod

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