FW: Namespaces and DTDs

len bullard cbullard at hiwaay.net
Fri Mar 12 05:26:40 GMT 1999

Didier PH Martin wrote:
> Hi
> I am using these simple rule of thumb:
> a) a XML DTD is useful for XML editors not for XML renderers
> b) Most XML renderers (XSL, CSS or DSSSL won't do document validation)
> c) a XML interpreter do not need a DTD (something else than rendition)
> If I need a DTD at the receiving end, then I am now no longer in the XML
> world but in the SGML world because the receiving end needs a validating
> parser. Several SGML parser like for instance SP can parse XML simplifyed
> DTD. The only simplification I gained is the -- or -0 think called omitags.
> Therefore, because I have to include a DTD for validation, better use then a
> SGML format.
> However, on the Web, to reduce complexity, I should not assume that the
> receiving end has a validating parser. Thus, because my XML document has
> been validated with my XML editor or by any other validation program. The
> receiving end makes the reasonnable assumption that if the docuement is a
> XML docuement it is "well formed" and valid.

That's mostly true because web documents don't stick around.  In 
cases where information is moving across multiple processes or sits 
in some long term archival, it is very handy to be able to validate it 
on the receiving end.  This will become more apparent to the XML
when they get to do the sort of work the SGML community did a decade
the first SGML applications fielded instances.   Things change.  Finding 
those changes quickly is the key to cheap rehosting.   In my experience,
DTDs die, someone gets to reinvent them and it will be painful.

Otherwise, yes, the DTD is much more useful in the editor in the initial 
part of the information lifecycle.


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