Active Directory provides predefined objects so that directory service manipulation can be uniform across namespaces. However, a Active Directory object in any given namespace might have more functionality than that specified by Active Directory. A namespace might also contain objects that are not defined at all by Active Directory. In addition, there are extensible directory services that allow their base schema to be modified and their objects to be arbitrarily extended by administrators and independent software vendors.
Object extensions are handled by the Schema Management Active Directory objects. These objects are used to:
the definitions of objects.
the definitions of objects.
In Active Directory, there are three ways to extend an Active Directory object:
in which providers expose additional, provider-specific objects in addition to the standard objects.
when clients add new objects and properties through a provider's extensible schema.
when clients attach new behavior (executable code) to an object definition.