external subset syntax

[Per-Ake Ling]

> From jjc at jclark.com Mon Dec 15 11:59:21 1997

> james anderson too wrote:

...[snip]

> > according to
> > [31]       extSubset  ::=   ( markupdecl | conditionalSect | PEReference
> > | S )
> > 
> > there is no requirement that the external subset begin with a document
> > type declaration.
> 
> It is a requirement that the external subset *not* begin with a document
> type declaration.
> 
If it were permitted, it would mean that there is a doctype declaration
within a doctype declaration, which is clearly nonsense. It is a common
misunderstanding that DTD means "document type declaration" instead of
"document type definition".

> > which would mean that the only indication of the root element type comes
> > from the refering declaration. which would mean that distinct xml
> > documents could well specify different root elements with respect to the
> > same external subset.
> > 
> > is this intentional?
> 
> Yes.
> 
Not only that, it is an underexploited feature in SGML that this is the
case. The only indication of real use of this feature in SGML comes from
Eliot Kimber, but I believe that it would be even more valuable in XML.

Per-Åke
--
Per-Åke Ling	(note: Per-Åke, transliteration Per-Ake)
email:	Per-Ake.Ling at uab.ericsson.se	phone:  +46  8 727 5674
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