ID/IDREF-like Definitions in the Schema itself

[Philip Nye]

Friedhelm Krebs wrote:
...
> My problem is, I want to define, which elements of a document are needed
> to calculate a sum, or to do any other operation. The result will be the
> content of an element, and the operation will be called, while I create
> the document instance.
...
> Is there any other possibility?

I'll have a go at this:

So far as I know, whilst proposed schemas allow much more complex
relationships to be expressed than a DTD, they are not up to expressing
this sort of constraint - "If element A takes a certain value or has
certain contents then element B over there must fit a particular model".

However, this is just the sort of thing which you can do very neatly
with XSLT - look for posts on "Crazy Idea" on this list in the last
couple of months for some leads.

Quoting from Rick Jelliffe:

> I have a note on "Using XSL as a Validation Language" at
> http://www.ascc.net/xml/en/utf-8/XSLvalidation.html also published in
> July Interchange magazine (ISUG).



Philip Nye
Engineering Arts UK

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