You can book a hotel out of a set of reserved hotel rooms (until Aug 1st) over Osnabrück's Congress Bureau. Please use the reservation form (PDF) for the KI-2007 conference! (Faxing it to the number given on the form is the preferred way of making your reservation.)
Upon receipt of the completed reservation form, the Congress Bureau will send you a confirmation, including details about the hotel. There is no extra charge for the reservation, and no deposit.