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 . <EOS>