Institute of Southern Punjab, Multan for database systems was produced in 1971 by the Data Base Task...
Transcript of 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: [email protected]
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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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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
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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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