The SCHEMA container object is used to attach a set of object definitions to a part of a namespace tree. Typically, each instance of a namespace will have it's own schema. Active Directory represents this by placing a SCHEMA container as a child of the namespace root.
Figure 5 - The SCHEMA Container
Figure 3 shows this typical layout. However, Active Directory does not limit schema containers to this level of the tree. A complex namespace might allow multiple schemas to exist in a namespace instance. In that case, SCHEMA containers might be found in other parts of a tree. There can only be one SCHEMA container in any given Active Directory container.
The SCHEMA container itself is a tree that contains class, property, and syntax definitions. New classes and properties can be created in the container to expand the schema.
Figure 6 - Schema Hierarchy
Non-extensible namespaces that do not have schema information embedded in the network should synthesize the schema container and prohibit the modification of its contents.