Institute of Southern Punjab, Multan for database systems was produced in 1971 by the Data Base Task...

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Institute of Southern Punjab, Multan

Mr. Muhammad Nouman FarooqBSC-H (Computer Science)

MS (Telecomm. & Networks)

Honors:

Magna Cumm Laude Honors Degree

Gold Medalist!

Blog Url: noumanfarooqatisp.wordpress.com

E-Mail: noman.iefr@hotmail.com

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Database Systems

Lecture# 2

Database Environment

Lecture 2: Database Environment

System Development Life Cycle (SDLC)

Database Development Process (DDP)

The Three-Level ANSI-SPARC Architecture

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System Development Life Cycle (SDLC)

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Database Development Process (DDP)

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Database Development Process (DDP)

Database Application development Process includes theFollowing Stages or steps:

1. Preliminary Study

2. Requirement Analysis

3. Database Design

4. Physical Design

5. Implementation

6. Maintenance

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Continued…

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Preliminary Study

Design of database is carried out in a number of steps; these steps

play important role in the design process and need to be given

proper attention.

First Phase of the database development process is the Preliminary

Study, which is based on the proper study of the system.

It means that all the parts of the systems, or the section of the

subject organization for which we intend to develop the system

must be studied.

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We should find the relation or interaction of different section of the

organization with each other and should understand the way

information flows between different sections of the organization.

Moreover it should also be made clear that what processing is

performed at each stage of the system.

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Requirement Analysis

Once we have investigated the organization for its different sections

and the way data flows between those sections; Detailed study of the

system is started to find out the requirements of each section.

In second phase, The detailed study of the system and its

functionality decisions made at this stage decide the overall activity

of the organization.

Requirements of one section of the organization are fulfilled in such a

way that all the sections in the organization are supporting each

other.12

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For example we can say that the results produced by the processing

taking place at one section are used as input for another section.

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Database Design

Third phase in the database development process is the database

design.

This is a technical phase of the process and need handsome skill as

a Database Administrator. This is the phase where the conceptual

design of the database is created. It also known as Conceptual Data

Modeling.

Entities are identified and given attributes, relationships are built

and different types of relationship are performed by assigning

cardinalities.14

Physical Design

In fourth phase, The choice of the DBMS is made on the basis of

requirements and the environment in which the system will operate.

Implementing a database on a specific DBMS is very important

because it involves the major financial investment of the

organization, and can not be reverted in case a selected DBMS in not

capable of providing the desired efficiency.

Also, Assigning meaningful Data Types, Constraints/Limitations and

De-Normalization of Data where required by the real time

scenario/system are to be finalized and processed in this phase.

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Implementation

This phase is specific to writing the application programs needed to

carry out different activities according to user requirements.

We must write application programs in this phase by using MySQL

(mai-structured query language) by using DBMS engine known as

XAMPP (Cross platform apache MySequel PHP Perl).

We can done coding with out any logical error; If we have

implemented all previous phases of database development process

correctly.

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Maintenance

Maintenance means to fine tune the system and check that the

designed applications systems are fulfilling the purpose for which

they are meant.

Also, this phase may involve designing any new application for the

enhancement of the system.

Or an already working application may need to be updated or

modified to remove any errors or to add some functionality in the

system.

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All these stages are necessary and must be given the necessary

attention at each level to get properly working and good system design

and a better working environment.

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The Three-Level ANSI-SPARC

Architecture

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The Three-Level ANSI-SPARC Architecture

An early proposal for a standard terminology and general

architecture for database systems was produced in 1971 by the Data

Base Task Group (DBTG) appointed by the Conference on Data

Systems and Languages (CODASYL, 1971).

The Data Base Task Group (DBTG) recognized the need for a two-

level approach with a system view called the schema and user views

called subschemas.

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The American National Standards Institute (ANSI) Standards Planning

and Requirements Committee (SPARC), ANSI/X3/SPARC, produced a

similar terminology and architecture in 1975 (ANSI, 1975). ANSI-SPARC

recognized the need for a three-level approach.

Although, The ANSI-SPARC model did not become a standard, It still

provides a basis for understanding some of the functionality of a

DBMS.

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The levels form a three-level architecture comprising an External,

Conceptual, and an Internal level.

The way users observe the data is called the External Level (Front

End). The way the DBMS and the Operating System perceive/stores

the data (Back End) is the Internal Level.

The Conceptual Level provides both the mapping and the desired

independence between the external and internal levels.

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The overall Description/Skeleton structure of the database is called the

database schema.

At the highest level, we have multiple external schemas (also called

subschemas) that correspond to different views of the data.

At the conceptual level, we have the conceptual schema, which describes

all the entities, attributes, and relationships together with integrity

constraints.

At the lowest level, we have the internal schema, which is a complete

description of the internal model, containing the definitions of stored

records, the methods of representation, the data fields, and the indexes

and storage structures used. There is only one conceptual schema and one

internal schema per database.

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The objective of the three-level architecture is to separate each

user’s view of the database from the way the database is physically

represented. There are several reasons why this separation is

desirable:-

1. Each user should be able to access the same data, but have a

different customized view of the data.

2. Users should not have to deal directly with physical database

storage details.

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4. The internal structure of the database should be unaffected by

changes to the physical aspects of storage, such as the changeover

to a new storage device.

5. The Database Administrator (DBA) should be able to change the

conceptual and database storage structures without affecting the

users’ views.

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A major objective for the three-level architecture is to provide data

independence, which means that upper levels are unaffected by

changes to lower levels.

There are two kinds of data independence: -

1. Logical Data Independence.

2. Physical Data Independence.

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1. Logical Data Independence: -

Changes to the conceptual schema, such as the

addition or removal of new entities, attributes, or relationships,

should be possible without having to change existing external schemas

or having to rewrite application programs. Clearly, the users for whom

the changes have been made need to be aware of them, but what is

important is that other users should not be.

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2. Physical Data Independence: -

Changes to the internal schema, such as using

different file storage structures, using different storage devices should

be possible without having to change the conceptual or external

schemas.

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Recommended Readings

Chapter 2 from: -

Modern Database Management – 8th Edition by Jeffery A. Hoffer,

Prescott and McFadden (Page No. 84-103)

Database Systems-A Practical Approach to Design, Implementation

and Management by Thomas Connolly and Carolyn BEGG, 4th Edition

(Page No. 69-114)

Fundamentals of Database Systems – 6th Edition by Elmasri and

Navathe (Page No. 58-83)

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Summary of Lecture

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Lecture 2➦

System Development Life Cycle (SDLC)

Database Development Process (DDP)

The Three-Level ANSI-SPARC Architecture

END OF LECTURE 2

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