Data Abstraction Concept

Data Abstraction Concept

 

         Data Abstraction Concept

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For a database system to be usable one user should

be able to retrieve data efficiently from it . The need

for efficiency has led designers of the database to

use complex data structures to represent data in the

database . Since many database system users are not

computer trained , developers ide the complexity from

users through several levels of abstraction which hide

the intricate details of the system but simplify users'

interactions with the system .

 

Physical Level Abstraction:

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The lowest level of abstraction describes how the

data are actually stored in the database system .The

physical level describes complex low-level data

structures in detail

 

Logical Level Abstraction:

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It is the next higher level of abstraction on top of the

physical level and it describes what data are stored in

the database and it also describes what relationship

exists among those data .Thus the logical level

describes the entire database in terms of a small

number of relatively simple structures and as such the

users of the logical level does not need to be aware of

the complexity . Database administrators who decide

what information to keep over the database use the

logical level of abstraction mostly

 

View Level Abstraction

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This is considered as the highest level of abstraction

of the database and it describes only part of the database.

Even though the logical level of the database

uses simpler structures , complexity always remains

because of the variety of information stored over the

large database .The view level of abstraction exists to

simplify the interaction of the system with the users .

The system may provide many views for the same

database and for multiple categories of users as well.