inclusions/exclusions/named groups

[Arjan Loeffen]

Andrea Anders wrote:

> 1) Neither SGML-inclusions nor -exclusions are allowed in XML!? How can I
>    express this in XML?

Inclusions and exclusions cannot be expressed by model group constructs (except
for a very few cases). As model groups describe and therefore affect an element's
content, and therefore are a DTD-based concept, exceptions describe and affect
the complete element subtree, and therefore are a document-instance-based
concept.

Best you can do is to merge inclusions into the model groups of all elements it
'intends to affect' (typically by defining parameter entities), which would
extent over all elements occurring in the model of the element you intended the
inclusion to work on (and elements in the model of those elements, etc.).

To alter the model group for exclusions requires you to re-think the complete set
of parameter entities used in the original DTD; you have to make certain that the
element you want excluded does not occurr in any model after entities are
resolved.

Unsupporting exceptions is the toll we pay for allowing standard parser
generators to be used to build XML systems.

Arjan.


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