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Database Architecture, Data Independence - Database Management - Lecture Slides, Slides of Introduction to Database Management Systems

Database Architecture, Data Independence, DBMS functionalities, Three levels, Objective, Physical representation, Refers to permanent structure are the main points of this lecture.

Typology: Slides

2011/2012

Uploaded on 11/03/2012

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dharmaraaj 🇮🇳

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Lecture - 3
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Database

Management

Systems

Lecture - 3

Lecture Overview

Database Architecture

Data Independence

Three Level

Architecture

A basis for understanding DBMS functionalities

Three levels at which data can be described

Objective

Separate users view from the physical representation

Why? Different views of same data Consolidated representation Both ways easy change

The Architecture

Depicted by three schemas or three models

Refers to permanent structure or intention of database

Level 1 External View

The way users think about data

External View

Users may have different views of the same data e.g. date, time etc.

External View

Virtual/calculated data: that is not actually stored in the database but is created when needed e.g. age, statistical data etc. Docsity.com

External View

User’s external view is created after considering data access, reports, and the transactions needs.

External View

External schema evolves as user needs are modified over time

Level 2 Logical or Conceptual View

A complete description of the information content of the database

Conceptual Schema

The entire information structure of the database, as seen by the DBA The community view of data

Conceptual Schema

Contains record types representing entities, data item types with their attributes, relationships and constraints on data.

Conceptual Schema

Contains Semantic information about the data meaning, security and integrity information