Method of authenticating a user in a heterogeneous computer environment. The method may include defining a set of unique prefixes, each prefix identifying a type of user repository; defining a set of abstract repository names, each abstract repository name identifying an address of a user repository; and authenticating the user in the heterogeneous computer environment by assigning a sequence comprising a unique prefix, a reference to an abstract repository name and a unique identifier for the user within the user repository indicated by the reference to the abstract repository name.