Mike's point is that it *shouldn't* fail, if the schema takes into
account the forward-compatibility mechanisms in XSLT 1.0, which say
that any element in the XSLT namespace is legal if the in-scope
version is more than 1.0.
The trouble with such a schema - at least, such an XML Schema schema -
is that it's not much use for checking real XSLT 1.0 stylesheets. It
can't reject
<xsl:text disable-output-escaping="on thursdays only">
for example.
Schema languages that allow co-constraints between different elements
and their attributes could do better.
-- Richard