RE: [xsl] Request help in understanding: node instance of schema-element(node)

> So, as I understand it, by adding the -val option SAXON 
> validates the XML input document against the XML Schema 
> specified by the stylesheet:
> 
>    <xsl:import-schema schema-location="test.xsd"/>
> 

It will also use any schema documents referenced in xsi:schemaLocation if
required.
 
> If validation succeeds, then the stylesheet can be certain 
> that the <test> element in the input document conforms to the 
> test element declaration in the XML Schema.

Correct.
> 
> And the stylesheet can check whether validation occurred and 
> succeeded by using this if-test:
> 
>    if (//test instance of schema-element(test)) then ...
> 
> Correct?

Yes. 
> 
> Thus, if the processor does not abort and the if-test fails it means:
> 
> -- The input XML document was not validated against the XML Schema.
> 
> There is no other reason for the if-test failing.
> 
> Correct?

Well, there are various other things that could go wrong, like there being
no test element, or there being more than one, but you're on the right
lines. 
> 
> The if-test is not requesting the processor perform run-time 
> validation of the <test> element against the XML Schema.
> 
> Correct?

Yes.
> 
> Is this the proper way to check <test> before operating on it?
> 
>    if (//test instance of schema-element(test)) then
>        //test * 2
>    else
>        if (//test castable as xs:integer) then
>            //test * 2
>        else
>            'Error'
> 

My preference is to use template rules. Or sometimes I use global variable
declarations:

<xsl:variable name="test-element" select="/test" as="schema-element(test)"/>

which acts as an assertion, causing the stylesheet to fail if not true
(provided $test-element is actually referenced, of course).

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