Schematron skeleton should be upgraded to support XSLT3 and XPath3.

There are three levels of support:

• The implementation should allow a schema/@queryBinding value of xpath3 and converts this to the appropriate xslt:stylesheet/@Version="3.0". That then enables the new xpath3 syntax. This can be done immediately, I think.

• We need to work out a proper Query Language binding for XSLT3. There are quite a few things in XSLT3 that require thought. For example, a big part is type safety. So I think an XSLT3 binding should support sch:let/@xsl:as (in the same way that xsl:key was introduced because it is a query-language-dependent feature.)

• We may need to figure out what the streaming story is for XSLT3. There is already a STAX QLB available, but would it be useful/necessary to have a query-language-binding subset of for "xslt3-streaming"