ใช้ในการอธิบายถึงรูปแบบและโครงสร้าง

Used to describe the format and structure of the data in the database by the database system does not depend on the actual structure of that database system, database users to see this information in the aspect, or view vary according to the purpose.Make the view in each level that can be separated from each other by a DBMS is Associate Manager at each level,

Used to describe the style and structure. The information in the database system. Without depending on the actual structure of the database itself. Database users to view data in this aspect or that vary according to the purpose , making the view in each level that can be separated into independent from each other by a DBMS to manage connections. In relation to each class

Used to describe the form and structure. Of system data base database. Without depending on the structure of the database Database user will see this information in different aspects or view the

.The perspective in each level that can be separated independently of each other, the DBMS static welding relationship in each level.