The xsl:document instruction creates a new document node. The content of the new document node
is created using the contained instructions (in the same way as xsl:result-document), and the new
document node is added to the result sequence. The instruction is useful mainly if you want to validate
the document: the element allows attributes validation and type which perform
document-level validation in the same way as the corresponding attributes on xsl:result-document.
The instruction also allows a function or template to create a temporary tree without the need to create a variable and then return the value of the variable.
This instruction should not be confused with the instruction of the same name in the XSLT 1.1 draft, (which
is supported in Saxon 6.5.x). That instruction was a precursor to xsl:result-document.
