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Subject: Re: Should empty elements allow whitespace?

James Clark scripsit:

> SGML with WWW amendment doesn't allow anything in an empty element (not
> whitespace, not entity references, not comments).  The XML 1.0 spec
> isn't very clear on this, but in the past the policy has been to
> maintain compatibility with SGML with respect to validity.

Speaking as a member of the XML Core WG, but *not* officially for it:

1) The WG believes that the XML rule is the same as the SGML one;

2) The use of the phrase "The declaration matches EMPTY and the
   element has no content" in the Element Valid VC, combined with the
   definition of "content", implies this;

3) The WG will almost certainly (IMO) issue an erratum in the next
   week or so, adding the phrase "(not even comments, PIs or white space)"
   to the above sentence.

> Being compatible with SGML/XML in this area would imply that TREX would
> not allow PIs and comments and entity references in an empty elements. 
> I believe that would be fundamentally wrong: validation behaviour should
> not as a matter of principle be affected by comments or entity
> structure.

I would agree with this, provided the term "empty" (which has a definite
SGML/XML meaning) were replaced with some other term such as "none".

> (It would also make it impossible to implement using just
> the standard SAX 2 interfaces, since these don't report internal entity
> references.)

That would be relevant only in the corner case of an entity containing
only whitespace/comments or nothing at all.  A reference to any other
sort of entity would clearly be incompatible with "empty" or "none".

John Cowan                                   cowan@ccil.org
One art/there is/no less/no more/All things/to do/with sparks/galore
	--Douglas Hofstadter

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