I actually haven't found a production implementation of APP ...
Uhm, yeah, I've been meaning to mention that; there are no production implementations of the APP. As a matter of fact, there are no implementations of the APP at all. Period. That's because the spec isn't finalized, and part of that finalization process will be the assignment of a URI for the "app:" namespace, which implies that every single implementation today has the wrong namespace for Service and Category documents.
Update: The new namespace has been minted:
For convenience, this protocol can be referred to as the "Atom Protocol" or "APP".
Posted by joe on 2007-06-13
Posted by Aristotle Pagaltzis on 2007-06-13
Posted by Mike Schinkel on 2007-06-14
Posted by Anne van Kesteren on 2007-06-16
I have no idea. Just like the Atom Syndication Format namespace URI, it just appeared, I'm not aware of who, when, where, why or how it came into existence.
Posted by joe on 2007-06-16
Posted by Mike Schinkel on 2007-06-12