top object class contains all possible attributes?

[dE]

From https://tools.ietf.org/html/rfc4512
   it
       can be said that an object class inherits the sets of *allowed* and
       required attributes from its superclasses

Therefore the top object class contains all possible attributes? OR

A subclasses cannot contain any attribute which is not included in it's 
superclass?

I'm running Apache directory studio, and I don't see that happening.