An object management system and data processing system which enable the containment relationships among a plurality of resource managers to be changed without affecting client applications which use services of those resource managers. A tree manager maintains tree structure data that defines the containment relationships among resource managers, together with identification data that is used to distinguish between them. From this tree structure data, an object manager builds a containment tree to grasp the containment relationships among the resource managers. When a client application issues an operation request to one of the resource managers, a message processor receives and forwards it to the object manager. The object manager then searches the containment tree to find identification data of a relevant resource manager for which the received operation request should be destined, thus sending the request to the found destination resource manager. This centralized approach of object management facilitates addition and removal of resource managers to/from the tree structure data.