How to validate the ContextItem in xquery - xquery

Question

My XSLT is primitive, my XQuery almost non existent, this should be trivial, so I wont post a whole example.
I have an XQuery, that I'm compiling and executing via the dotnet saxon9ee-api
import schema default element namespace "" at "MessingAbout.xsd";
for $v in (validate { doc("MessingAbout.xml") })/element(SQUARE,FILLEDSQUARETYPE)
return <OUTPUT>{$v/#colour}</OUTPUT>
which works very nicely.
I want to use the "ContextItem" though, so I can query different XMLS, and I've got this to work, by setting the ContextItem in the XQueryEvaluator to a document.
import schema default element namespace "" at "MessingAbout.xsd";
for $v in /SQUARE
return <OUTPUT>{$v/#colour}</OUTPUT>
but I'd like to validate the contextItem and then use that do use things like element(SQUARE,FILLEDSQUARETYPE)...but how do you do this?

Answer 1

I'm not quite sure what you're attempting to do, but given "MessingAbout.xsd":
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
elementFormDefault="qualified">
<xs:complexType name="FILLEDSQUARETYPE">
<xs:attribute name="colour" type="xs:string"/>
</xs:complexType>
<xs:element name="SQUARE" type="FILLEDSQUARETYPE"/>
</xs:schema>
and "MessingAbout.xml":
<SQUARE colour="red"/>
your first query produces <OUTPUT colour="red"/>, which I assume is what you expect. To use the context item in the second query, I rewrote it as:
import schema default element namespace "" at "MessingAbout.xsd";
for $v in (validate { . })/element(SQUARE,FILLEDSQUARETYPE)
return <OUTPUT>{$v/#colour}</OUTPUT>
and passed the source document on the command line: -q:test2.xq -s:MessingAbout.xml.
That gives me the same result as the first query. I hope that's helpful.

Answer 2

As well as the approaches suggested by Martin and Norm, you have the option of doing the validation in the calling application, e.g. Java or C#. Build the document using a s9api DocumentBuilder with validation options set, and then pass the resulting typed XdmNode as the context item when running the query. This approach is preferable if you want to do more with the validated document than just running one query. But if you do it this way, it's useful for the query to assert that it's expecting a validated document, which you can do with a "declare context-item" in the query prolog.