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Re: questions about element declarations



At 06:35 AM 24/9/96 +0100, W. Eliot Kimber wrote:

>>* Should XML prohibit the use of inclusion and exclusion exceptions in
>>element declarations? (11.2.4, 11.2.5)?
>
>Yes.  Exclusions are, with very rare exceptions, a bad thing, causing much
>more trouble than they're worth. Inclusions, while expressing a useful
>semantic, also cause more trouble then they're worth and require DTD
>processing.

Exclusions are very useful for prohibiting nesting of objects in OR groups
that are shared, such as those typically found in  %text; parameter entites.
For example:

<!ENTITY % text   (#PCDATA|a|b|c)>

<!ELEMENT p (%text;)>
<!ELEMENT a (%text;) -(a)>

I cannot agree that they are "a bad thing">
----
Martin Bryan, The SGML Centre, Churchdown, Glos. GL3 2PU, UK 
Phone/Fax: +44 1452 714029   WWW home page: http://www.u-net.com/~sgml/