A sliding door system has a pair of horizontally opposed vertical surfaces defining therebetween an opening, an upper horizontal surface connecting uppermost ends of the vertical surfaces, a lower horizontal surface connecting lowermost ends of the vertical surfaces, and a door moving horizontally to open and close the opening. Then, the proxy server selecting server notifies the client of the IP address of the most approximate server to the client in place of the IP address of the server, based on the physicallogical location information, and if necessary, the periodically obtained load information of the proxy servers. This fact makes the data valuable as data in two ways. The classifiers with individuality improve classification accuracy, for example, when used as classifiers in a classifier array. That wireless access point then uses that surrogate Internet Protocol address along with its own Internet Protocol address to facilitate establishing one or more data tunnels as necessary to support the communication needs of the mobile station. The detailed characteristics of prediction errors generated during lossless image compression encoding or decoding process are retrieved and fed back to a halftone print mode of the printer and are used to adjust the halftone print mode.