RDF 1.1 Turtle - examples

Hello,
 
I am a beginner to RDF and Turtle so I try hard to study the official documents published by W3C
and learn the principles described there.
 
As far as I understand from the RDF 1.1Turtle document there are missing lines to define the empty
prefix in examples 24 and 26.
I would expect something like this:
 @prefix : <http://example.org/stuff/1.0/> .
 
Or am I wrong?
 
Kind regards,
Martin Cerny