Red Hat DIRECTORY SERVER 8.1 - DEPLOYMENT Deployment Manual page 58

Chapter 4. Designing the Directory Tree
Figure 4.10. Examples of a Flat and an Organizationally-Based DIT
Using a hierarchical DIT, a deployment must then determine the subject domain of the hierarchy. Only
one choice can be made; the natural tendency is to choose the organizational hierarchy.
This view of the organization serves well in many cases, but having only a single view can be very
limiting for directory navigation and management. For example, an organizational hierarchy is fine
for looking for entries that belong to people in the Accounts department. However, this view is much
less useful for finding entries that belong to people in a geographical location, such as Mountain
View, California. The second query is as valid as the first, yet it requires knowledge of the attributes
contained in the entries and additional search tools. For such a case, navigation via the DIT is not an
option.
Similarly, management of the directory is much easier when the DIT matches the requirements of
the management function. The organization of the DIT may also be affected by other factors, such
as replication and migration considerations, that cause the DIT to have functional utility for those
applications but very little practical utility in other cases.
From the above discussion, it is clear that hierarchies are a useful mechanism for navigation and
management. To avoid the burden of making changes to an existing DIT, however, a deployment may
elect to forgo a hierarchy altogether in favor of a flat DIT.
It would be advantageous for deployments if the directory provided a way to create an arbitrary
number of hierarchies that get mapped to entries without having to move the target entries in question.
The virtual DIT views feature of Directory Server resolves the quandary of deciding the type of DIT to
use for the directory deployment.
Virtual DIT views provide a way to hierarchically navigate entries without the requirement that those
entries physically exist in any particular place. The virtual DIT view uses information about the entries
to place them in the view hierarchy. To client applications, virtual DIT views appear as ordinary
container hierarchies. In a sense, virtual DIT views superimpose a DIT hierarchy over a set of entries,
irrespective of whether those entries are in a flat namespace or in another hierarchy of their own.
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