OSF DCE Application Development Guide--Introduction and Style Guide

Using the DCE Name Service
By setting a namespace up this way, however, you do not necessarily restrict yourself to
this one model for accessing binding information. Through the use of two other types of
entry, groups and profiles, which can be superimposed on the simple object model, you
can set up models where clients bind to abstractions such as services, or directly to the
servers themselves. These techniques are described in the next section.
Nevertheless, at this point you have enough information to set up a namespace that
consists of an entirely flat expanse of separate resource entries. Bindings can be
imported by clients by looking up specific names. If the client has no specific name to
look up, or if the lookup on the name(s) it has fails, it has no alternative way of binding
to a server.
5.11 Groups and Profiles
Name lookups can be made more flexible with two other types of entry; namely, groups
and profiles.
5.11.1 Group Entries
A group entry consists essentially of multiple independent other entries whose names are
also associated under the group name. These other entries can be simple (single-name)
entries, or they may themselves be group entries. Doing an import from the group entry
will return the contents (the binding handles) of its included entries (which are called
members), but the selection is made by the DCE RPC runtime, and from the client’s point
of view is undefined and implementation dependent.
In practice, the way this works with the usual binding import operations is as follows.
Clients normally import bindings by first calling rpc_ns_binding_import_begin() to set
up an import context. Once this is done, successive calls to
rpc_ns_binding_import_next( ) will return binding handles from namespace entries
until the handles have all been returned or the client decides to stop; the client decides
which handle(s) to use based on its own criteria. When it is finished importing, it calls
rpc_ns_binding_import_done( ) to free the context.
The kind of entry the information is returned from is usually unknown to the client,
which needs to know only a name to look up and the interface UUID by which it wants
to bind. If the name is that of a simple server entry, then the bindings contained in that
entry only will be returned. If the name is of a group entry, then bindings will be
returned from members (single entries) of the group, selected (by the RPC runtime) in an
undefined order. If one or more members of the group are themselves groups, then the
same thing happens recursively whenever these lower-level groups are accessed.
Note that the group entry and its members are separate things. The group entry can be
deleted, but its former members will continue to exist as independent entries, unless they
too are explicitly deleted. Thus, you can implement a namespace organization where the
same bindings can be imported through individual simple entries or through group
124246 Tandem Computers Incorporated 5− 19