The advent of network-based directory services did not totally obviate the need for local configuration data. As much as it was necessary to make networks of machines work well together, it was also necessary for computers to be able to work well in standalone situations. Open Directory solves this problem by using a set of domains:

These features enable Mac OS X to run just fine in standalone mode while allowing it to be configured to run in large network environments. It can work well in enterprise-wide configurations with multiple platforms that are woven together with various standards. Interoperability has been the Holy Grail for many network administrators. With its range of directory integration, Mac OS X is a first-class citizen in such environments.