Three Level ANSI SPARC Database System

ANSI SPARC model mainly divided into three parts: Internal level, Conceptual level, and  External level

1) Internal level

• Lowest level of data abstraction.
• It describes how data are actually stored in a physical storage devices.
• Also known as physical level.
• Internal view is described by internal schema, contains following information:
• how space allocation is performed for new data
• which file system is used to store data
• whether data compression or data encryption is used to store data

2) Conceptual level

• Middle level of data abstraction.
• It describes what data are stored in database, what relationship exist among them and security constraints.
• Also known as logical level.
• Conceptual view is defined by conceptual schema, describes all records and relationship.

3) External level

• Highest level of data abstraction.
• It describes view (some part of database) to a particular user that he/she need.
• Also known as view level.
• External view is described by external schema, contains definition of logical records, relationship in view and method of deriving view from conceptual view.