How annotations are stored in RdfDB

Hi all,
I was browsing the annotations DB for the Annotea server
I installed and I noticed that Fragments is not used...

From [1] I was thinking that the following uri
     http://www.w3.org/2000/10/annotation-ns#Annotation
would be stored as follows:

     Uris      <--- http://www.w3.org/2000/10/annotation-ns
     Fragments <--- Annotation

while what I see in current implementation of W3C Annotea
is taht:
     Uris      <--- http://www.w3.org/2000/10/annotation-ns#Annotation

Is this an implementation choice for annotations?
Have I completely misundestood [1]?
And what about Strings...

Any insight is welcome :-)

Bye
Enrico

[1] http://www.w3.org/1999/07/13-persistant-RDF-DB

PS: I once thought that
     Revisions <--- /2000/10/
but I thisnk this is definiitely false...