FNS reserves for its own use all the atomic names listed in Table 22-1 as namespace identifiers. For example: _orgunit, org, _site, site, and so forth. This limitation applies to contexts in which the namespace identifiers can appear, as defined by the arrangement of namespaces in "Structure of the Enterprise Namespace". FNS does not otherwise restrict the use of these atomic names in other contexts.
For example, the atomic name service is used as a namespace identifier relative to a user name, as in user/fatima/service/calendar, to mean the root of user fatima's service namespace. This does not preclude a system from using the name service as a user name, as in user/service, because FNS specifies that the context to which the name user/ is bound is for user names and not for namespace identifiers. In this case, service is unambiguously interpreted as a user name. On the other hand, you should not create a directory named user because /user/mikhail would cause confusion between the user mikhail and the file (or subdirectory) /user/mikhail.