Exchange Server - Active Directory Schema

1) What is known as "Exchange Server - Active Directory Schema" ?

• Active Directory provides you with a way of extending the schema.
• This differs from the Exchange Server 5.5 Schema, which does not allow you to add new classes or attributes.
• To write applications that access Active Directory, it is useful to have an understanding of the Active Directory schema.
• The directory schema is a collection of descriptions, or rules, that define characteristics of objects in the directory.
• The schema defines available object classes in the directory, relationships between object classes, attributes of each object class, and specific characteristics of attributes and classes