RE: [xsl] design question on function namespaces

["Michael Kay" <mike@xxxxxxxxxxxx>]

>     <xsl:template match="open-office:chapter" 
>     mode="doc:chapter-has-footnotes"
>     as="xs:boolean">
>       <xsl:sequence select="exists(.//footnote)"/> </xsl:template>
> 
> 1. Return the boolean value to whom | what?
> 

To its caller. For example,

<xsl:variable name="x" as="xs:boolean">
  <xsl:apply-templates select="chap" mode="doc:has-footnotes"/>
</xsl:variable>

If the call on apply-templates returns a boolean, that boolean will be the
value of variable $x.

We all tend to think in terms of the 1.0 model where XPath expressions read
the source document and XSLT instructions write to the result tree. Thanks
largely to Jeni Tennison's intervention half way through the 2.0 design
process, that's no longer the processing model: instructions and expressions
now both return results to their caller, and the result can be any sequence
of atomic values or nodes.

There are basically two ways of getting the result of an XSLT instruction
back into the XPath world to make it available for further processing: you
can assign it to a variable, as above, or you can return it as the result of
a function, as in my earlier example:

<xsl:function name="doc:has-footnotes" as="xs:boolean">
  <xsl:param name="chap" as="element()"/>
  <xsl:apply-templates select="$chap"/>
</xsl:function> 

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