xml-dev - Re: XSchema Spec Section 2.2, Draft 1

["Michael Kay" <M.H.Kay@eng.icl.co.uk>]

>Peter Murray-Rust wrote:
>
>> Unless there is
>> sensible running text whose prime purpose is to be read
by humans there is
>> no particular value in having mixed content (i.e. strings
+ elements mixed).
>
Counter-example from GedML (adapted to make it
self-explanatory):

<PERSON>
<NAME>Frederick BLOGGS
   <SOURCE>Birth Certificate</SOURCE>
   <CONFIDENCE>High</CONFIDENCE>
   <CHANGED>
        <ON>12 Jan 1983</ON>
        <BY>MHK</BY>
   </CHANGED>
   <NOTE>Generally signed himself "Frederik"</NOTE>
</NAME>

The general form is that the "attributes" of an object are
represented by the content of a first-level child element,
and qualifiers to the attributes (source, confidence level,
alternative values, etc) are represented by grandchild
elements.

This is a direct translation of the GEDCOM metamodel. I have
come across similar things in medical data models where the
aim is to record opinions rather than facts: in such a model
we need to record "facts about facts about facts": e.g.
"John says that his mother told him that his father died of
a heart attack".

Unfortunately I am unable to declare in the DTD that the
element contains "PCDATA content followed by zero or more of
the following child elements", XML's peculiar rules mean
that with mixed content I cannot declare any ordering or
cardinality constraints. (I wonder if someone thought that
there was no requirement?)

Mike Kay


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