fns - overview of FNS
Federated Naming Service (FNS) provides a method for
federating multiple naming services under a single, simple
interface for the basic naming operations. The service sup-
ports resolution of composite names, names that span multi-
ple naming systems, through the naming interface. In addi-
tion to the naming interface, FNS also specifies policies
for composing names in the enterprise namespace. See
fns_policies(5) and fns_initial_context(5).
Fundamental to the FNS model are the notions of composite
names and contexts. A context provides operations for:
o associating (binding) names to objects
o resolving names to objects
o removing bindings, listing names, renaming and so on.
A context contains a set of names to reference bindings. A
reference contains a list of communication end-points. Every
naming operation in the FNS interface is performed on a con-
The federated naming system is formed by contexts from one
naming system being bound in the contexts of another naming
system. Resolution of a composite name proceeds from con-
texts within one naming system to those in the next, until
the name is resolved.
XFN is X/Open Federated Naming. The programming interface
and policies that FNS supports are specified by XFN. See
xfn(3XFN) and fns_policies(5).
A composite name is a name that spans multiple naming sys-
tems. It consists of an ordered list of components. Each
component is a name from the namespace of a single naming
system. FNS defines the syntax for constructing a composite
name using names from component naming systems. Individual
naming systems are responsible for the syntax of each com-
The syntax for composite names is that components are com-
posed left to right using the slash character ('/') as the
component separator. For example, the composite name
.../Wiz.Com/site/Oceanview.East consists of four components:
..., Wiz.COM, site, and Oceanview.East. See
fns_policies(5) and fns_initial_context(5) for more exam-
ples of composite names.
FNS is useful for the following reasons:
o A single uniform naming interface is provided to
clients for accessing naming services. Consequently,
the addition of new naming services does not require
changes to applications or existing naming services.
Furthermore, applications that use FNS will be port-
able across platforms because the interface exported
by FNS is XFN, a public, open interface endorsed by
other vendors and by the X/Open Company.
o Names can be composed in a uniform way (that is, FNS
supports a model in which composite names are con-
structed in a uniform syntactic way and can have any
number of components).
o Coherent naming is encouraged through the use of
shared contexts and shared names.
FNS and Naming Systems
FNS has support for NIS+, NIS, and files as enterprise-level
naming services. This means that FNS implements the
enterprise-level policies using NIS+, NIS, and files. FNS
also supports DNS and X.500 (via DAP or LDAP) as global nam-
ing services, as well as support for federating NIS+ and NIS
with DNS and X.500. See the corresponding individual man
page for information about the implementation for a specific
nis+(1), xfn(3XFN), fns_dns(5), fns_files(5),
fns_initial_context(5), fns_nis(5), fns_nis+(5),
fns_policies(5), fns_references(5), fns_x500(5)
Man(1) output converted with