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Explore the three essential levels of ANSI-SPARC Architecture in databases - External, Conceptual, Internal - and grasp the significance of data models, languages, software components, and multi-user DBMS architecture.
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Database Environment Chapter 2
The Three-Level ANSI-SPARCArchitecture • External Level • Conceptual Level • Internal Level • Physical Data
External Level • The users view of the database. This level describes that part of the database that is relevant to the user
Conceptual Level • The community view of the database. This level describes what data is stored in the database and the relationships among data. • This level represents • All entities and their attributes and their relationships • The constraints on the data • Semantic information about the data • Security and Integrity of Information
Internal Level • This level describes the physical representation of the data on the computer. • Schemas, mapping and instances • Data Independence • Logical data independence ( Immunity of the external schema to changes in the conceptual schema) • Physical data independence ( Immunity of the conceptual schema to changes in the internal schema_
Database Languages • The Data Definition Language • The Data Manipulation Language • Procedural DML • Nonprocedural DML • Fourth Generation Languages • Form Generators, Report Generators, Graphics Generators, Application Generators
Data Models and Conceptual Modeling • Data Model – An Integration collection of concepts to describe and manipulate data • Object-Based Data Models • Entity-Relationship • Semantic • Record-Based Model • Relational • Network • Hierarchical
Components of a DBMS • Query processor • Database Manager • File Manager • DML processor • DDL complier • Catalog Manager
Software Components of the Database Manager • Authorization Control • Command Processor • Integrity Checker • Query Optimizer • Transaction Manager • Schedule • Recover Manager • Buffer Manager
Multi-User DBMS Architecture • Teleprocessing • File-Server • Client-Server
System Catalogs • A Repository of Information describing the data in the database
Functions of a DBMS • Storage, Retrieval and Update • A User-accessible catalog • Transaction Support • Concurrency Control and Services • Authorization Services • Support for Data Communication • Integrity Services • Services to Promote Data Independence • Utility Services