xml/xslt component in Mozilla/Firefox

Hello

I would like to known if the xml/xslt component is the same in the 
Mozilla distribution and in the Firefox distribution. Is there only one 
development effort, used by the two browsers ?
And then, can we say the level of the Mozilla XML/XSLT features is equal 
to the level of Firefox XML/XSLT features ?

Difficult to find in the documentation...

thanks in advance

Frédéric Laurent