[Owncloud] What app 'types' are valid ?

[Christian Reiner]

Hello all, 
inside the appinfo/info.xml file some apps specify a <types> section holding 
the apps 'types'. This is stored in the database upon installation of the app 
and can be used later to load only apps of a certain type at runtime. 

I found several apps claiming to be of type "filesystem", one of type 
"authentication". 

My question: is there a definition or collection of valid types ? 
These are _not_ the categories offered at the apps.owncloud.org site which is 
a pretty strange selection anyway. Or are the 'types' just made up by the app 
developers by best knowledge and intention?

Christian