> It seems exclude-result-prefixes needs to be explicity set 
> for each imported stylesheet, rather than using the value in 
> the importing stylesheet - is that right?

Yes, it's scope is the stylesheet module.

> 
> Is there any reason why the exclude-result-prefixes value 
> isn't taken from the importing stylesheet?  Not the biggest 
> issue I know, just struck me as odd.
> 

The only reasons I can think of are (a) to avoid a lot of complexity in
defining the rules for how it interacts with import precedence, (b) to
improve modularity, in the sense that the behaviour of a module is
controlled within that module.

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