A flush bolt mechanism to be mounted into a recess at the vertical edge of an inactive door of a pair of swinging doors. A first sub-volume is assigned to a de-duplication domain and a first content summary is computed for the first sub-volume. The PC includes a PC communication unit receiving information related to the communication status from the projector, a beacon analyzing unit analyzing the received information and a display output unit displaying a result of the analysis by the beacon analyzing unit. Since the air introduction for keeping the negative pressure at an adequate value is carried out in a region in a gaseous phase in the container, no leakage of ink occurs, and air is reliably introduced. Embodiments include converting recursions into repetitions, demoting imbedded compound repetitions from element declarations having imbedded compound repetitions, and demoting imbedded leaves from elements having imbedded leaves.