Logical design vs physical design

1. Class Assignment

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CLASS ASSIGNMENT - 1
PHYSICAL DESIGN & LOGICAL DESIGN

Course Name: System Analysis & Design
Course Code: SE 606

Submitted by:
Md.Mahedi Mahfuj -BIT 0207
Mostafizur Rahman -BIT 0211
Md.Habibur Rahman -BIT 0216

Submitted to:
Awsaful Islam
Course Instructor
(System analysis & design)

Date of submission:
21
st
July, 2012


Institute of Information Technology
University of Dhaka

2. Class Assignment

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SYSTEM DESIGN:

System design is the process of defining the architecture, components, modules, interfaces and
data for a system to satisfy specified requirements. System design is therefore the process of
defining and developing systems to satisfy specified requirements of the user.

TYPES OF SYSTEM DESIGN:

There are two types of system design mainly. They are,

Physical Design

Logical Design


They are explained below in brief:


PHYSICAL DESIGN:

The physical design is a graphical representation of a system showing the system’s internal and
external entities, and the flows of data into and out of these entities.
An internal entity is an entity (person, place, or thing) within the system that transforms data.
Internal entities include, for example, accounting clerks (persons), departments (places), and
computers (things). Whereas, an external entity is an entity (person, place, or thing) outside the
system that transforms data.
Actually, the physical design relates to the actual input and output processes of the system. This
is laid down in terms of how data is given as an input into a system, how it is authenticated, how
it is processed, and how it is displayed as output. Put another way, the physical portion of
systems design can generally be broken down into three sub-tasks:
1. User Interface Design
2. Data Design
3. Process Design

User Interface Design is concerned with how users add information to the system and with how
the system presents information back to them.
Data Design is concerned with how the data is represented and stored within the system.

3. Class Assignment

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Finally, Process Design is concerned with how data moves through the system, and with how
and where it is validated, secured and/or transformed as it flows into, through and out of the
system.
To use an analogy, a personal computer's physical design involves input via a keyboard,
processing within the CPU, and output via a monitor, printer, etc. It would not concern the actual
layout of the tangible hardware, which for a PC would be a monitor, CPU, motherboard, hard
drive, modems, video/graphics cards, USB slots, etc. It involves a detailed design of a user and a
product database structure processor and a control processor.
Therefore we can say that, physical design specifies where, how, and by whom a system’s
processes are accomplished. A physical design does not tell us what is being accomplished.

LOGICAL DESIGN:
The logical design of a system pertains to an abstract representation of the data flows, inputs and
outputs of the system. This is often conducted via modeling, using an over-abstract (and
sometimes graphical) model of the actual system.
Logical design is a graphical representation of a system showing the system’s processes and the
flows of data into and out of the processes. We use logical design to document information
systems because we can represent the logical nature of a system-what tasks the system is doing,
without having to specify how, where or by whom the tasks are accomplished. What a system is
doing will change less over time than how it is doing it.
To represent the logical design of a system we can use different diagrams like Entity-
Relationship Diagram. In this way, we can furnish an abstraction of the total system through
logical design in an orderly explanatory way.

CONCLUSION:
So, we can come to a conclusion from the above explanation that logical design of a system is
actually an abstraction of the data flows, inputs and outputs whereas, physical design is actually
related to the actual input and output processes of the system, total absence of abstraction here. It
is laid down in terms of how data is given as an input into a system, how it is authenticated, how
it is processed, and how it is displayed as output.


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