In distributed system for operating devices in association with one another, a device responsible for determining whether or not an access is permitted, and criteria for determination are hidden from accessing device or user, and flexible access control is provided among devices without need for previously defining accessible devices or user's identifiers. Communication process opens data communications which are interactions between devices to permit indefinite number of other devices to monitor data. A behavior monitoring process acquires interaction within particular device or between other devices in system for storage in behavior log table. Access control process matches the behavior log table with access control policy to determine whether or not device should be associated with target device from which process request is received, or with a target device to which a process program of the particular device attempts to access.