> So to be bold, how can I correctly create a key expression to 
> read out all members of a key, or list them in some other way?

For 

<xsl:key name="N" match="M" use="U"/>

you can find all the members of the key using select="//(M)". There's no way
of finding them via the key itself.

(The term "members of the key" isn't actually meaningful, but I think I can
guess what you might mean.)

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