One of the advantages of NSS mentioned above is that it can be extended
quite easily. There are two ways in which the extension can happen:
adding another database or adding another service. The former is
normally done only by the C library developers. It is
here only important to remember that adding another database is
independent from adding another service because a service need not
support all databases or lookup functions.
A designer/implementor of a new service is therefore free to choose the
databases s/he is interested in and leave the rest for later (or
completely aside).
