Servlets and LDAP - Developing Java Servlets - page 158

A Brief Discussion of Directories

A directory provides a method of persistence where information can be organized and searched
quickly. This might sound similar to the relational databases that you are used to; however,
there are some fundamental differences.

The most noticeable difference is the way the stored information is organized. In a relational
database, information is stored in tables that are interconnected using foreign keys that refer-
ence a related table. The structure of the information stored in a directory is quite different.
The information is stored in more of a hierarchy that provides a logical relationship between
the objects. The informational structure will look something like Figure 11.1.

o = Airius.com

ou = Groups ou = People

cn = Tad Hans
sn = Hans
givenName = Tad
uid = thans
mail = [e-mail]
telephoneNumber = [phone]
pager = [phone]

cn = Bob Smith
sn = Smith
givenName = Bob
uid = bsmith
mail = [e-mail]
telephoneNumber = [phone]

cn = Managers
uniqueMember = uid=thans, ou=People, o=Airius.com
description = The Bosses

F IGURE 11.1
Organization of the data stored in a directory.

The following notes summarize the other differences between a directory and a relational data-
base:

• Directories are more suitable for environments where the data is being read quite a bit

and is not being modified often.

• Directories generally come with a preexisting schema.

• Directories do not support complex joining during searches like a relational database.

• Directories have better support for substring searches and for searching on similarities.

• Directories are usually quicker and easier to configure and manage than relational data-

bases. They are generally less expensive also.