RE: [xsl] reading a document into a typed variable

Subject: RE: [xsl] reading a document into a typed variable
From: "Michael Kay" <mike@xxxxxxxxxxxx>
Date: Fri, 2 Oct 2009 09:33:32 +0100
> I don't understand the difference between two ways of loading 
> an XML file into a variable (see A and B below). Case A used 
> to work with old saxon 8.9, but with 9.2 only B is 
> successful. With A I get following error message:
>   XTTE0570: Required item type of value of variable $global.setup is
>   document-node(element(global-setup, xs:anyType)); supplied 
> value has item type xs:string

Saxon's type checking has improved between the two releases. Saxon 9.2
recognizes at compile time that if $global.setup.file is a string, then
trace($global-setup-file, x) will also be a string, and that this is
inconsistent with your declared type, which is document-node(). In earlier
releases this error would only have been detected at run-time, and only if
this branch of the if-then-else were selected. But Saxon's static
type-checking is not yet perfect: it seems it is failing to spot that if
trace($global-setup-file, x) is a string, then <xsl:copy-of
select="trace($global-setup-file, x)"/> will also be a string, and this is
why you get no compile-time error message for case B. I'll take a look at
this and try to improve it for the next release.

What you really want is to remove the error, of course, and to do that you
need to ensure that the exception branch of your conditional delivers a
result that is consistent with the type declaration of the variable.


Michael Kay 

> If I omit the type declaration in A, the rest of the 
> stylesheet is nevertheless working correctly. So at a certain 
> stage, what saxon sees as a xs:sting is converted into a tree.
> It's OK with me if you just point me to the right 
> documentation to find out myself.
> Thanks for clarification,
> Georges
> [A]
> > <xsl:param name="global.setup.file" 
> > select="'../../xml-resolved/GlobalSetup-resolved.xml'" 
> > as="xs:string"/> <xsl:variable name="global.setup" select="if
> > (doc-available($global.setup.file))
> >                                           then
> > document($global.setup.file)
> >                                           else 
> > trace($global.setup.file,'Configuration File $global.setup.file was 
> > not readable (missing or not valid)!')"
> > as="document-node(element(global-setup))"/>
> [B]
> >
> > <xsl:variable name="global.setup" 
> > as="document-node(element(global-setup))">
> >   <xsl:choose>
> >     <xsl:when test="doc-available($global.setup.file)">
> >       <xsl:copy-of select="document($global.setup.file)"/>
> >     </xsl:when>
> >     <xsl:otherwise>
> >       <xsl:copy-of select="trace($global.setup.file,'Configuration
> > File $global.setup.file was not readable (missing or not 
> valid)!')"/>
> >     </xsl:otherwise>
> >   </xsl:choose>
> > </xsl:variable>
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