1. A computer-readable medium having stored thereon a data structure for containing version information of a software item, comprising: a first data field containing data representing a version-independent identifier that is unchanged by revisions and upgrades performed on the software item; a second data field containing data representing a version-specific identifier that is unchanged by revisions but changed by upgrades performed on the software item; and a third data field containing data representing a revision number that is increased by each revision performed on the software item.