Directory objects are the skeleton of the namespace. When arranged into a tree- like structure, they divide the namespace into separate parts. You may want to visualize a directory hierarchy as an upside-down tree, with the root of the tree at the top and the leaves toward the bottom. The topmost directory in a namespace is the root directory. If a namespace is flat, it has only one directory, but that directory is nevertheless the root directory. The directory objects beneath the root directory are simply called "directories":
A namespace can have several levels of directories:
When identifying the relation of one directory to another, the directory beneath is called the child directory and the directory above is called the parent directory.
Whereas UNIX directories are designed to hold UNIX files, NIS+ directories are designed to hold NIS+ objects: other directories, tables and groups. Each NIS+ domain-level directory contains the following sub-directories:
Technically, you can arrange directories, tables, and groups into any structure that you like. However, NIS+ directories, tables, and groups in a namespace are normally arranged into configurations called domains. Domains are designed to support separate portions of the namespace. For instance, one domain may support the Sales Division of a company, while another may support the Manufacturing Division.