 The consequences of unauthorised software versions finding their way into the live environment can be serious.Typically, in a mature organisation, stringent Change and Release Management processes will exist to prevent this occurring, but such processes require a place where the authorised software versions can be safely stored and accessed.The solution put forward by ITIL in its third version is called the Definitive Media Library or DML (replacing the previously named Definitive Software Library or DSL in version two).