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Re: PEReferences in ElementDecls (Parsing of DTDs)

• From: "Chris Olds" <colds@n...>
• To: "Falk, Alexander" <falk@i...>,<xml-dev@i...>
• Date: Fri, 18 Dec 1998 16:09:19 -0800

You ask:
>So the question is: is the XML-grammar inside the XML 1.0 Spec incomplete?
>Is there a new version? What rules do need to be adapted to allow for
>PEReferences?


The answer is found just after production [28] in the XML spec:
================================
Document Type Definition
[28]  doctypedecl ::=  '<!DOCTYPE' S Name (S ExternalID)? S? ('['
(markupdecl | PEReference | S)* ']' S?)? '>'
[29]  markupdecl ::=  elementdecl | AttlistDecl | EntityDecl | NotationDecl
| PI | Comment

The markup declarations may be made up in whole or in part of the
replacement text of parameter entities. The productions later in this
specification for individual nonterminals (elementdecl, AttlistDecl, and so
on) describe the declarations after all the parameter entities have been
included.
================================
Tim Bray's (excellent) annotation on this says (in part) "This little
paragraph is awfully important. [...] the grammar describes what the text
looks like after [parameter entities ]have all been expanded." (full text is
at http://www.xml.com/axml/notes/PEs-1.html ).

Another easily overlooked gotcha about PEs is that they can be used for
parts of a markupdecl ([29]) (e.g. all or part of a content model) in the
external part(s) of a DTD, but can only replace an entire markupdecl in the
internal portion of a DTD.

    /cco



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