[xsl] referring to base output URI in xsl:document-result

[Helka Folch <hfolch@xxxxxxx>]

How can I refer to the base output URI in the href attribute of  the 
document-result XSLT element?

I would like to have a template that uses the output URI specified in a 
parameter. If no parameter is specified, it uses the base output uri.

I tried the following  using an empty string as value of href to refer 
to the base output uri but it doesn't work  :

<xsl:template match="doc">
   <xsl:param name="outputFile"  select="''"/>
   <xsl:result-document  href="{$outputFile}"/>

               ...

   </xsl:result-document>
</xsl:template>


(I also tried  specifying  "."  as the default value of the parameter, 
but this refers to the base output uri directory, not to the output uri 
itself)

Thanks a lot.

Helka Folch