A schema is the set of directory server rules that define the structures, contents, and constraints of a Directory Information Tree (DIT). The schema guarantees that any new data entries or modifications meet and conform to these predetermined set of definitions. It also reduces redundant data definitions and provides a uniform method for clients or applications to access its Directory Server objects.

The PingDirectory Server ships with a default set of read-only schema files that define the core properties for the Directory Server. The Administrative Console provides a Schema Editor that administrators can use to view existing schema definitions and add new custom schema elements to their DIT. Any attempt to alter a schema element defined in a read-only file or add a new schema element to a read-only file will result in an "Unwilling to Perform" result.