passing parameters to an xsl-file

I am using xalan and want to pass a parameter to my stylesheet, that should
be available everywhere in my sheet.
I tried to declare the param as a top level element, but with
1) <xsl:param name="paraname" select="output"/>
my param doesn't even seem to have a value
and with
2) <xsl:param name="paraname">output</xsl:param>
it had a value, but I was not able to change it (with a "  -PARAM paraname
'output'   "command from the command line as recommanded for xalan as a
first try)

I guess the problem is that I did not quite get the concept of this params
yet.
Thanks to anybody who can give me a hint.

Martin



 XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list