dynamically generated XSL that needs to include namesp

I am using a stylesheet to generate XSL within an xsl:document command.

The problem I have is that I want to include the xmlns:str namespace to my
generated stylesheet so that I can use the EXSLT string function
uri-decode().

As the namespace is not added automatically, and it is illegal to add a
namespace using the <xsl:attribute> command, I can't see any way to do this.
Any suggestions, or is this a brick wall? 

thanks,

Yves Jaques 
Information Officer     FIDI 
FIDI - room F-320 
United Nations Food and Agriculture Organisation 
viale delle Terme di Caracalla - 00100 Roma - ITALIA 
_________________________________________ 
yves.jaques@xxxxxxx 
tel. : (39) 0657056058        fax.: (39) 0657052476    
Please visit our web site at: 
HTTP://WWW.FAO.ORG/FI