Federated Naming Service

In computing, the Federated Naming Service (FNS) or XFN (X/Open Federated Naming) is a system for uniting various name services under a single interface for the basic naming operations. It is produced by X/Open and included in various Unix operating systems, primarily Solaris versions 2.5 to 9.
The purpose of XFN and FNS is to allow applications to use widely heterogeneous naming services (such as NIS, DNS and so on) via a single interface, to avoid duplication of programming effort.
Unlike the similar LDAP, neither XFN nor FNS were ever popular nor widely used. FNS was last included in Solaris 9 and was not included with Solaris 10.