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Problem in E15

From: Dieter Köhler <dieter.koehler@ppp.uni-bamberg.de>
Date: Fri, 06 Jul 2001 18:18:22 +0200
Message-ID: <3B45E4CE.721B278@ppp.uni-bamberg.de>
To: xml-editor@w3.org
The sentence in E15 which states:

"The declaration matches EMPTY and the element has no content (not even entity
references, comments, PIs or white space)."

should be replaced by:

"The declaration matches EMPTY and the element has (after replacing any entity
references with their replacement text) no content (not even comments, PIs or
white space)."

Reason:  The original wording requires extraordinarily complicated validity
checks:  While validity checks for the other contentspec types can be performed
after resolving all entity references, this is not be possible for elements
declared EMPTY, because entity references of the from <!ENTITY foo ""> would go
through unnoticed:

...
<!ENTITY foo "">
<!ELEMENT empty EMPTY >
...
<empty>&foo;</empty>

This is even worse, since if testing for entity references makes sense in the
above example, there is no reason, why it should not make sense for recursively
defined entity declarations such as:

...
<!ENTITY foo "">
<!ENTITY bar "<empty>&foo;</empty>">
<!ENTITY doc "<doc>&bar;</doc>">
<!ELEMENT empty EMPTY >
...
&doc;

"&doc;" can only be validated correctly if an XML processor keeps track of every
entity reference resolve operation during analyzing the DTD.  This would
disallow simple parser strategies such as e.g. mentioned in XML spec App. D,
where "the XML processor will recognize the character references when it parses
the entity declaration, and resolve them before storing the ... string as the
value of the entity ...", because if the parser stores the string for "bar"
which is "<empty></empty>" it will pass the validity check, though it was
defined as "<empty>&foo;</empty>".

-- 
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Received on Friday, 6 July 2001 12:20:48 GMT

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