nXML questions

[Sam Steingold]

Now that nXML is the default xml mode instead of the old sgml-mode, I am 
wondering it its manual could be brought up to date, e.g., answering the 
question which bothers me right now:

how do I tell nxml that I have a compound docbook document consisting of a few 
files included into the master file using system entities, when editing a 
component file? nxml does not recognize any of the entities, defined in the 
master file.

also, nxml seems to think that the <code> element and the language= attribute 
of the <programlisting> element are invalid. why?

also, it does not recognize <xi:include> elements. why?

thanks!

Sam.