RE: [xml-dev] XML Schema co-occurrence constraint workaround

> Here's a potential workaround for the co-constraint problem 
> in XML Schema.
...
> 
> This technique is far from ideal as it involves modifying the 
> source

A refinement of this technique is to add the xsi:type attribute using a SAX
filter; you then pipe your original source into the schema validator via the
filter. Quite a few of the limitations of XML Schema 1.0 can be overcome by
validating not the original document, but a simple transformation of it.

Michael Kay
http://www.saxonica.com/