To answer a question I was asked recently: XPS documents contain metadata too.

As mentioned in diary entry Analyzing XPS files, XPS files follow the Open Packaging Conventions specification. They contain file _rels/.rels (looking inside with zipdump.py):

Making it more readable with xmldump.py:

File _rels/.rels informs us that docProps files contain metadata.

Didier Stevens
Senior handler
Microsoft MVP
blog.DidierStevens.com DidierStevensLabs.com