Three-Schema Architecture

Three-Schema Architecture

Internal schema   (one view)
describes physical storage structures
access paths, indexes used
Typically uses a physical data model

Conceptual schema at the conceptual level ( one view)
describes the logical structure and constraints for the whole database for a community of users
Uses a conceptual or an logical data model

External schemas (many view) 
Many views describe how users see data 
Information about schemas is stored in the system catalog