Introducing Active Directory - MCTS Guide to Microsoft Windows Server 2008 Active Directory Configuration - page 83

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Figure 3-5 The Active Directory Users and Computers window

Before you can go too far in working with Active Directory, knowing something about the
information you find in the database is helpful. Active Directory's contents and the functions it
performs in your network are defined by the schema, objects, and Group Policy Objects (GPOs,
discussed later in this chapter in “Introducing Group Policy”).

The Active Directory Schema
All information in the Active Directory database is organized as objects. An object is a grouping
of information that describes a network resource, such as a shared printer, or an organizing
structure, such as a domain or OU. The schema defines the type, organization, and structure of
data stored in the Active Directory database and is shared by all domains in an Active Directory
forest. The information the schema defines is divided into two categories: schema classes and
schema attributes. Schema classes define the types of objects that can be stored in Active
Directory, such as user or computer accounts. Schema attributes define what type of information
is stored in each object, such as First name, Last name, and Password for a user account object.
The information stored in each attribute, such as “Mary” in the First name attribute, is called
the attribute value .
Figure 3-6 shows the relationship between schema classes, attributes, and Active Directory
objects. As you can see, some schema attributes, such as the Description attribute used for both
objects, can be shared by more than one Active Directory object. When Active Directory is first
installed, a default schema describes all available default objects, but you can extend this schema
to add attributes to existing object classes or create new object classes.
This discussion of Active Directory refers to several different object classes in Active
Directory. Figure 3-7 shows object classes and their associated icons in Active Directory Users
and Computers. Active Directory objects can be organized into two basic groups, discussed in
the next sections: container objects and leaf objects.