Explicitly closed world "not"

{ ?x a RegisteredAttendee.
  ?x :homepage ?p.
  ?p log:semantics ?F.
  ?F log:notIncludes { ?x a :Vegetarian }.
} 
=>
{ ?x a :Omnivore }. 

If an attendee's homepage doesn't say they are a vegetarian, then they are a non-vegetarian.