rcp uses composite names such as sirius:/usr/jsmith/memo, which has two components: the host name sirius and the file name (path) /usr/jsmith/memo. The mail program uses composite names such as jsmith@altair, which has two components: the user name jsmith and the host name altair.
Each application defines its own composition rule for names, parses the composite names, and resolves composite names. Composition rules often differ from one application to another.
Without FNS, the user must remember which applications permit composite naming and which do not. For example, the composite name sirius:/tmp/saleslist is accepted by the rcp command, but not by the cp command.
Without FNS, the user must also remember the different composition rules used among different applications. Applications that support composite names on their own can use only a small and specific set of naming systems, and must be changed whenever a new type of naming system is added.
Incorporating a uniform policy for composite naming into the computing platform permits any application to support composite names in a uniform way. The application passes one name to one interface.