A system comprising: a first relay device provided on a first network hierarchy level; and a second relay device provided on a second network hierarchy level higher than the first network hierarchy level, wherein the first relay device includes a first information reception unit configured to receive target object information about a target object, the target object information being transmitted by a radio tag attached to the target object in accordance with a predetermined timing; a first information storage unit configured to store the target object information received by the first information reception unit; characterized in that the first relay device further includes a first change determination unit configured to determine whether there has been a change in a status of the target object, based on a status of reception of the target object information by the first information reception unit; and a first information transmission unit configured to transmit the target object information about the target object to the second relay device, when the first change determination unit determines that there has been the change in the status of the target object. a first relay device provided on a first network hierarchy level; and a second relay device provided on a second network hierarchy level higher than the first network hierarchy level, wherein the first relay device includes a first information reception unit configured to receive target object information about a target object, the target object information being transmitted by a radio tag attached to the target object in accordance with a predetermined timing; a first information storage unit configured to store the target object information received by the first information reception unit; characterized in that the first relay device further includes a first change determination unit configured to determine whether there has been a change in a status of the target object, based on a status of reception of the target object information by the first information reception unit; and a first information transmission unit configured to transmit the target object information about the target object to the second relay device, when the first change determination unit determines that there has been the change in the status of the target object. a first information reception unit configured to receive target object information about a target object, the target object information being transmitted by a radio tag attached to the target object in accordance with a predetermined timing; a first information storage unit configured to store the target object information received by the first information reception unit; characterized in that the first relay device further includes a first change determination unit configured to determine whether there has been a change in a status of the target object, based on a status of reception of the target object information by the first information reception unit; and a first information transmission unit configured to transmit the target object information about the target object to the second relay device, when the first change determination unit determines that there has been the change in the status of the target object. a first change determination unit configured to determine whether there has been a change in a status of the target object, based on a status of reception of the target object information by the first information reception unit; and a first information transmission unit configured to transmit the target object information about the target object to the second relay device, when the first change determination unit determines that there has been the change in the status of the target object.