1. A computer system for managing a configuration item to be associated with a plurality of other configuration items, the system comprising: a repository that holds, for each configuration item, one set of data indicating at least one predetermined attribute of the configuration item and a relationship with another configuration item; a discovery section to detect information on the configuration items; a determining section to determine, from the information detected by the discovery section, an association of a first configuration item with a second configuration item and an association of the first configuration item with a third configuration item; and a data creating section to create, from one set of data of the first configuration item, common data including an attribute common to an attribute of the first configuration item associated with the second configuration item and an attribute of the first configuration item associated with the third configuration item and plural derived data items including an attribute that is not common thereto and a relationship with another configuration item, wherein the common data and the plural derived data are stored in the repository.