Draft Spec mark 2

[Eric Zurcher]

At 09:40 6/09/2000 +1100, Greg Whitbread wrote:
>Mixed content might also impact some of the validation
>and context issues discussed earlier.
>
> From http://www.w3.org/TR/1998/REC-xml-19980210 ,
> Extensible Markup Language (XML) 1.0.
> "An element type has mixed content when elements of that type may contain
>  character data, optionally interspersed with child elements. In this case,
>  the types of the child elements may be constrained, but not their order or
>  their number of occurrences:"
>

Greg,

While validation of mixed content is indeed a problem when using XML 1.0
DTDs, XML Schema can handle it. Quoting from
http://www.w3.org/TR/xmlschema-0/ , XML Schema Part 0: Primer (W3C Working
Draft, 7 April 2000)

"Note that the mixed model in XML Schema differs fundamentally from the mixed
 model in XML 1.0. Under the XML Schema mixed model, the order and number of
 child elements appearing in an instance must agree with the order and number
 of child elements specified in the model. In contrast, under the XML 1.0
 mixed model, the order and number of child elements appearing in an instance
 cannot be constrained. In sum, XML Schema provides full schema validation of
 mixed models in contrast to the partial schema validation provided by XML
 1.0."

While mixed content is best avoided, I'd hate to rule it out completely. In
particular, it might be good if those elements or attributes containing
blobs of text could also contain some embedded HTML (or, rather, XHTML)
markup, to allow for italics, sub- and super-scripts and so on.


Eric Zurcher
CSIRO Division of Entomology
Canberra, Australia
E-mail: ericz at ento.csiro.au