I did what you suggested, thanks for the helpful reply. Although it's
not the perfect fit for what I needed, it's the only possible way to
make my xsd work right now.

S. Huseyin Ulger (dontspam) wrote:
> The constraint you are looking for can not be achieved using XSD schemas.
> Only work around is using xsi:type attribute[1] to define the type of the
> element in the instance document and defining different types in the schema
> as you need it.
>
> Although Schematron supports these kind of constraints, Microsoft xml
> validators do not support Schematron at this time.
>
> [1] http://www.w3.org/TR/xmlschema-1/#xsi_type
>
> --
> S. Huseyin Ulger [MSFT]
> MSXML Dev
>
>
> "Duarte S" wrote:
>
> > Hi,
> > Is it possible, in a W3C schema, to constraint the structure of
> > elements based on attribute values? For example:
> >
> > <instr type="sql" instruction="SELECT * ....." />
> > <instr type="exec" command="C:/work.bat" parameters="/p /s" />
> >
> > In this example, the attribute 'type' is allways present, however the
> > other attributes depend on the value of the 'type' attribute
> > ('instruction' is only present if type="sql", etc...). Is it possible
> > to apply such a constraint within a W3C Schema?
> >
> > I've read in another topic that this kind of constraint could be made
> > with a Schematron Schema. If so, is it possible to do a W3C Schema with
> > embedded Schematron rules? How are these rules applied?
> > 
> > Thanks
> > 
> > Duarte
> > 
> >