> In XSLT 1.0 the xsl:sort attribute 'select' states it's an expression
> which includes variable bindings, so I assumed that ;
> 
>   <xsl:variable name="title" select="'title'" />
>   <xsl:sort select="$title" />
> 
> would be equal to ;
> 
>   <xsl:sort select="title" />

No, it's equivalent to

<xsl:sort select="'title'"/>

Variables in XSLT contain values, not XPath expressions or parts thereof.

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