Hello Martin,
> Are you saying that a schema should define or
> reference xml:lang and xml:id attributes?
Yes, a schema should reference the standard xml:lang and xml:id attributes.
> the instance documents should use those
> attributes as much as possible?
Yes, instance document should make liberal use of xml:lang and xml:id.
> As for the DOM getElementById making use of xml:id attributes in an
> instance document, a test with http://jsfiddle.net/ady5P/ shows that
> only Opera supports that, Firefox, Chrome, IE 9, Safari don't do that.
Oh! Thanks for letting me know.
> As for your pattern example <xs:pattern value="[-]*" />, the
> character  is not allowed in XML 1.0 documents which most schemas
> likely are these days.
Yes, true. However, I did specify 1.1 in my schema:
<?xml version="1.1"?>
Thanks!
/Roger