CHAPTER ONE
THE SYSTEM DEVELOPMENT
ENVIRONMENT
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INTRODUCTION
Information systems analysis and design is a
complex, challenging, and stimulating
organizational process that a team of business
and systems professionals uses to develop and
maintain computer-based information systems.
ISAD is an organizational improvement
process.
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INTRODUCTION
Systems analysis and design is a proven methodology
that helps both large and small business reap the
rewards of utilizing information to its full capacity.
The systems development life cycle (SDLC) is central to
the development of and efficient information system.
We will highlight four key SDLC steps.
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INTRODUCTION
Planning and selection
Project identification and selection
Initiating and planning
Analysis
Requirement determination
Requirement structuring
Design, and
Implementation and operation.
Be aware that these steps may vary in each organization
depending on its goals.
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System Analysis and
Design
The major goal of ISAD is to improve organizational systems.
(manual or automated)
Often this involves developing or acquiring application software and training
employees to use it.
Application software, also called a system, is designed to support a
specific organizational function or process, such as inventory
management, Registrar software….
The goal of application software is to turn data into information.
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System Analysis and
Design
In addition to application software, the
information system includes:
The hardware and systems software
Documentation and training materials, The specific job
roles associated with the overall system,
Controls, which are parts of the software written to help
prevent fraud and theft.
The people who use the software in order to do their job
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System and its
Components
A system is an interrelated set of components
with an identifiable boundary, working
together for some purpose.
A system has nine characteristic.
1. Components
2. Interrelated components
3. A boundary
4. A purpose
5. An environment
6. Interface
7. Input
8. Output
9. Constraints 7
System and its
Components
A system is made up of components
A component is either an irreducible part or an
aggregate of parts, also called a subsystem.
The simple concept of a component is very powerful.
Just as with an automobile, we can repair or upgrade the
system by changing individual components without having to
make changes throughout the entire system.
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System and its
Components
The components are interrelated; that is, the
function of one is somehow tied to the functions
of the others.
A system has a boundary, which in which all of its
components are contained and which establishes
the limits of a system, separating the system from
other systems.
Components with in the boundary can be changed
whereas things outside the boundary cannot be
changed
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System and its
Components
All of the components work together to achieve some
overall purpose for the larger system: the system's
reason for existing.
A system exist with in an environment- everything
outside the system’s boundary.
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System and its
Components
Usually the system interacts with its environment,
exchanging, in the case of an information system, data
and information.
The points at which the system meets its environment
are called interfaces, and there are also interfaces
between subsystems.
Because an interface exists at the point where system
interact its environment, the interface has several
special, important function.
An interface provides:
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System and its
Components
Security, protecting the system from undesirable elements
that may want to infiltrate it.
Filtering unwanted data, both for elements leaving the system and
entering it
Encoding and decoding incoming and outgoing messages
Detecting and correcting errors in its interaction with the
environment
Buffering, providing a layer of slack between the system
and its environment, so that the system and its environment
can work at different speeds.
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System and its
Components
Because interface functions are critical in
communication between system components or a system
and its environment, interfaces receive much attention
in the design of information system.
You will spend a considerable portion of time in
systems development dealing with interfaces:
especially interfaces between an automated system and its
users and interfaces between different information systems.
It is the design of good interfaces that permits different
systems to work together without being too dependent
on each other.
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System and its
Components
A system must face constraints in its functioning
because there are limits on:
what it can do and how it can achieve its purpose within its
environment.
Some of these constraints are imposed inside the
system (a limited number of staff available) and others
are imposed by the environment (due dates or
regulation) 14
System Concepts
Once we have recognized something as a system and
identified the system’s characteristics, how do we
understand the system?
Further, what principles or concepts about systems
guide the design of information systems?
A key aspect of a system for building systems is the
system’s relationship with its environment.
Some systems, called open systems, interact freely with
their environments, taking in input and returning output.
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System Concepts
As the environment changes, an open system must
adapt to the changes or suffer the consequences.
A closed system does not interact with the
environment; changes in the environment and
adaptability are not issues for a closed system.
However, all business information system are open, and in
order to understand a system and its relationships to other
information systems, to the organization, and to the larger
environment, you must always think of information systems
as open and constantly interacting with the environment.
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System Concepts cont…
There are several other important systems concepts
with which systems analysts need to become familiar:
Decomposition
Modularity
Coupling
Cohesion
In addition you need to understand the difference between
viewing a system at a logical and at a physical level:
each with associated description concentrating on different aspects
of a system.
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System Concepts cont…
Decomposition deals with being able to break down a
system into its components.
These components may themselves be systems (subsystem)
and can be broken down into their components as well.
Decomposing a system allows us to focus on one
particular part of a system,
This makes it easier to think of how to modify that one part
independently of the entire system.
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System Concepts cont…
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System Concepts cont…
Finally, cohesion is the extent to which a subsystem
performs a single function.
A logical system description portrays the purpose and
function of the system without tying the description to
any specific physical implementation.
The physical system description, on the other hand, is a
material depiction of the system, a central concern of
which is building the system.
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Fundamentals of Information
Systems
An information system (IS) is a set of interrelated
elements or components that collect (input),
manipulate (process), and disseminate (output) data
and information and provide a feedback mechanism
to meet an objective.
In information systems:
Input is the activity of gathering and capturing raw data
processing involves converting or transforming data into
useful outputs.
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Fundamentals of
Information Systems
Output involves producing useful information,
usually in the form of documents and reports.
In information systems, feedback is output that is
used to make changes to input or processing
activities.
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Types of Information System Overviews
Until now we have talked about information systems
in generic terms, but there are actually several
different types or classes of information systems.
These classes are distinguished from each other on the
basis of:
what the system does or by the technology used to
construct the system.
You are responsible to determine which kind of
system will best address the organizational problem
or opportunity on which you are focusing.
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Classification of Systems
System can be classified based on the
following categories
Natural Vs Manmade or Artificial systems
Open Vs Closed Systems
Simple Vs Complex Systems
Stable Vs Dynamic Systems
Permanent Vs Temporary Systems
Deterministic vs. Probabilistic Systems
Types of Information System Overviews
As a systems analyst working as part of a
team, you will work with at least 4 classes of
information systems:
Transaction processing systems
Management Information Systems
Decision support systems (for individuals,
groups, and executives)
Expert systems
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Types of Information System Overviews
Transaction Processing System
A transaction processing system (TPS) automates the
handling of data about business activities or transactions.
Data about each transaction are captured, transaction are
verified and accepted or rejected, and validated
transactions are stored.
Reports may be produced immediately to provide
summaries of transactions.
The analysis and design of a TPS requires you to focus on
the firm’s current procedures for processing transactions.
How does the organization track, capture, process, and output
data?
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Management Information System
A Management information system (MIS) a computer
based system that takes the raw data available through a
TPS and converts them into a meaningful report
/aggregated report form.
E.g. The MIS system can therefore direct the manufacturing
department on what to produce and when.
Developing an MIS calls for a good understanding:
what kind of information managers require
Management information systems often require data from
several TPS
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Decision Support System
A decision support system (DSS) is designed to help
decision makers with decisions by combining data,
sophisticated analytical models and user-friendly
user interface.
A DSS provides an interactive environment in which
decision makers can quickly manipulate data and
models of business operations. (What if?)
A DSS has three parts.
A database
Mathematical or graphical models of business processes.
A user interface (or dialogue module)
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Decision Support
System
DSS software supports certain decision-
making activities (from problem finding to
choosing a course of action).
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Expert Systems
An expert system is a computer based system that
contains knowledge of experts in a particular domain.
If-then-else rules or other knowledge representation
forms describe the way an expert would approach
situations in specific domain of problems.
The focus on developing an ES is acquiring the
knowledge of the expert in the particular problem
domain.
Knowledge engineers perform knowledge acquisition;
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System and System Analyst- A
key resource
A systems analyst(s) facilitates the development of
information systems and computer applications.
The systems analyst performs systems analysis and design.
Systems analysis is the study of a business problem
domain for the purpose of recommending
improvements and specifying the business requirements
for the solution.
Systems design is the specification or construction of a
technical, computer-based solution for the business
requirements identified in a systems analysis.
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System and System Analyst- A
key resource
Organization change themselves to combat
their environment.
Whenever organizations change themselves
they will also change their business process,
hence their information system as well.
Changing the information system require a
system analyst.
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Who is a systems analyst?
In simple terms, systems analysts are people who
understand both business and computing.
Systems analysts study business problems and
opportunities and then
Transform business and information requirements of the
business into the computer-based information systems.
The system analyst also bridges the communications
gap between those who need the computer and those
who understand the technology.
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Who is a systems analyst?
The role of systems analyst is splitting into two
distinct positions or roles, business analyst and
application analyst.
A business analyst (more of analyst)is a systems analyst
that specializes in business problem analysis and
technology-independent requirements analysis.
An application analyst (more of designer ) is a systems
analyst that specializes in application design and
technology-dependent aspects of development.
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Skills of a System Analyst
Problem-solving skills
Take a large business problem, break down that problem
into its component parts, analyze the various aspects of the
problem, and then assemble an improved system to solve
the problem.
Interpersonal communications skills
analyst must be able to communicate effectively, both
orally and in writing.
Interpersonal relations skills
systems analysts must be extroverted or people-oriented.
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Skills of a System Analyst
Systems analysis and design skills
Systems analysis and design skills can be
conveniently factored into three subsets:
Concepts and principles
Tools
Techniques
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Personal Qualities and Knowledge
required
Working knowledge of Information Technology
The analyst must be aware of both existing and emerging information
technologies and techniques so that he can show end-user and
management how new technologies can benefit their business and its
operations.
Computer Programming and Experience
They must know how to program because they are the principal link
between business users and computer programmers.
General Business Knowledge
Systems analysts should be able to communicate with business experts to
gain knowledge of problems and needs.
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Personal Qualities and Knowledge required
Project management
Effectively managing projects is crucial to a systems analyst’s job.
Flexibility and adaptability
There is no single, magical approach or solution applicable to systems
development.
Character and ethics
The nature of the systems analyst's job requires a strong character and
sense of ethics.
Systems analysts gains assess to sensitive and private data and
information about customers, suppliers, employees, and the like
The analyst must be very careful not to share such feelings or
information with the wrong people.
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