document()

I want to open an xml file that resides in a folder that is a above the xsl 
file in which document() is used (to access the xml file).
The XSL file resides here (under the web root):
/mickel/XSL/PC/

and the XML file resides here (under the web root);
/mickel/XML


I have tried to use document(/mickel/XML/xml_file.xml), but it doesn't seem 
to work. Should this work? Can I reference the web root folder with "/"?


/Gabriel