Use of '&' in element of XML Document

Paul Grosso pgrosso at
Wed Jul 28 01:43:48 BST 1999

At 19:15 1999 07 27 -0400, John E. Simpson wrote:
>At 05:20 PM 07/27/1999 -0500, Paul Grosso wrote:
>>You cannot redeclare & which is one of XML's predefined
>>entities [1].  Just use & in place of &--no declaration
>>is necessary.
>Actually, that's not 100% true: while & is a pre-defined entity, the
>questioner expressly mentioned that he/she wanted to use a DTD. As the
>second paragraph of the REC's section that you pointed to says:
>	All XML processors must recognize these entities whether they are 
>	declared or not. For interoperability, valid XML documents should 
>	declare these entities, like any others, before using them. 
>I believe the word "valid" there says that you can reliably use them
>without declaration only in well-formed documents. If you want an
>interoperable DTD, they've got to be declared. 

Provided that you take "redeclare" to mean defining it differently
than its pre-definition, what I said is 100% true.  You cannot 
redeclare pre-defined entities, and no declaration is necessary.

Use of a DTD does not imply validity.  DTDs can be used in the
well-formedness case too.  And, per the paragraph you quote, it 
is true that such entities need not be declared in either the
valid or well-formed case.  ("For interoperability" and "should" 
does not change the statement made in the first sentence of the
paragraph you quote.)  And, the rest of the paragraph after you
ended your quote goes on to say:

  If the entities in question are declared, they must be declared 
  as internal entities whose replacement text is the single character
  being escaped or a character reference to that character, as
  shown below. 

And the following table gives the pre-definitions.  The original
response to this question showed a different declaration for amp,
and that would not be allowable.


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