The schema defines the shape and format of entries in the GDS directory. It contains four types of rules, which describe the following:
· The legal hierarchy of entries. What entries may be subordinate of other entries. These rules are what prevents, for example, countries from being subordinate to states.
· The allowable object classes, the mandatory and optional attributes of entries, and which attributes are the naming attributes.
· The allowable attribute types, associating a unique OID and an attribute syntax with each attribute type.
· The syntaxes of attributes that describe what attribute values look like, such as strings, numbers, or OIDs.
By installing the proper schema, an entry of any particular object class can have the two attributes needed to identify a cell. See the OSF DCE Administration Guide for a full description of how to set up a cell entry using either GDS or DNS.