element census tool?

I know I could write this myself, but suspect someone else has already 
done a better job of it - and I just don't know the right Google 
keywords to summon it.

I'm looking for a tool that I can feed an XML document, and it will tell 
me which element names were used in the document.

Attributes used on those elements would be a bonus, as would a frequency 
count for usage, but mostly I'm just trying to survey a collection of 
(DocBook) documents quickly.

All suggestions welcome.

-- 
Simon St.Laurent
http://simonstl.com/