> I define a variable $y containing an Xpath expression laike this :
> 
> 	<xsl:variable name="y" select"'@my_attribute'">
> 
> Calling
> 	 <xsl:value-of select="dyn:evaluate(., $y)"/>
> works fine and give me the attribute value.
> 
> The problem I have is that when I define $y like this :
> 
> 	<xsl:variable name="y">@num</xsl:variable>
> 
> (Which is to me exactly the same definition as before)
> then I get a error !
> The HTML page cannot be loaded. 

The two expressions are not at all the same. In one, the variable is a
string, in the other it is a result tree fragment. XPath automatically
converts a result tree fragment to a string when required (probably at
considerable cost), but Javascript does not.

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