Provided is a document-management server that controls the amount of change notifications sent to an administrator of an image-processing server in the case where metadata necessary for system cooperation is changed. The image-processing server acquires an attribute of specific metadata from document data and transmits the attribute together with the document data. The document-management server manages the document data based on the attribute of the specific metadata transmitted from the image-processing server. A metadata-setting-receiving unit receives a change in the specific metadata. A notification-priority-adding unit adds a notification priority to the specific metadata for which a change is received by the metadata-setting-receiving unit. A change-notifying unit creates a change notification for informing that the specific metadata has been changed, and transmits the created change notification to an administrator of the image-processing server at a transmission timing based on the notification priority.