"Universal Schema Reference":

Directory Server Object Classes
Releases 1.x, 3.x, and 4.0


subschema
Supported by Directory Server 3.x, 4.0
Definition Object class that stores all the attributes and object classes for a given directory server (whereas, attributeTypes is used to store all attributes known to the server and objectClasses is used to store all object classes known to the server). Directory server 4.0 has one subschema entry, cn=schema. This subschema entry can be modified to add and remove schema dynamically.
Superior Class top
OID 2.5.20.1


Required Attributes	Description
objectClass	Specifes the objects for this object class.


Allowed Attributes	Description
attributeTypes	Attribute types used within a subschema.
cn (commonName)	Common name of the object class. For the Netscape Directory Server, this value is always cn=schema.
dITContentRules	Defines directory tree content rules used within a subschema.
dITStructureRules	Defines directory tree structure rules used in a subschema.
matchingRuleUse	Identifies the attribute types to which a matching rule applies in a subschema.
matchingRules	Defines matching rules used in a subschema.
nameForms	Defines the name forms used in a subschema.
objectClasses	Defines the object classes used in a subschema.