2.3. Three-level ANSI-SPARC Data Base Architecture

For the first time in 1971, Database Task Group (DBTG) appointed by the Conference on Data Systems and Languages (CODASYL), produced a proposal for general architecture for database systems. The DBTG proposed a two-tier architecture as shown in Fig. 2.1 (a) with a system view called the schema and user views called subschemas. In 1975, ANSI-SPARC (American National Standards Institute – Standards Planning and Requirements Committee) produced a three-tier architecture with a system catalog. The architecture of most commercial DBMSs available today is based to some extent on ANSI-SPARC proposal.

ANSI-SPARC three-tier database architecture is shown in Fig. 2.6. It consists of following three levels: ...

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