Identifying XML Document Types (was XML media types revisited)

W. Eliot Kimber eliot at
Fri Jan 15 22:01:58 GMT 1999

At 04:24 PM 1/15/99 -0500, Simon St.Laurent wrote:
>Schemas may be a good answer (if they kill the internal subset escape
>hatch), combining an assertion about document type with a way to check it.
>Is there any comparable 'architecture validation' process?  Or are they
>just assertions?

Yes--validation of a document against its architectural DTD (a component of
the overall architecture definition) is defined and is, not surprisingly,
just like normal SGML/XML validation.  Validation against the other
(non-SGML/XML) components of the architecture definition is not defined by
the architecture standard, so at that point you're where you would be with
other schema mechanisms).

>The only (obvious, anyway) flaw with these options are the need to load the
>document before you know if it's worth processing - but that may be seen as
>more a flaw of today's limited filesystems and transfer protocols, I suppose.

You only have to scan the document for the declaration, you don't have to
process the whole thing. In the architecture PI spec, we explicitly require
that the PI occur before the document instance for this very reason.

It's really no different from "magic numbers" in graphics files or the XML
character set declaration--you have to have a little bootstrapping knowledge.


<Address HyTime=bibloc>
W. Eliot Kimber, Senior Consulting SGML Engineer
ISOGEN International Corp.
2200 N. Lamar St., Suite 230, Dallas, TX 75202.  214.953.0004

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