© 2005 Prentice Hall1-1 Stumpf and Teague Object-Oriented Systems Analysis and Design with UML

© 2005 Prentice Hall 1-1

Stumpf and TeagueObject-Oriented Systems Analysis and Design with

UML

.

PART ONEI ntroduction to

I nform ation System Developm ent


Stumpf and TeagueObject-Oriented Systems Analysis and Design with

UML

.

Chapter 1I ntroduction


Learning Objectives

• Explain how systems thinking helps address the complexity of developing an information processing system.

• Define a system and identify the function, components, and structure of familiar systems.

• Understand the relationship between a system and its environment or context.

• Explain the role of an interface.• Give examples of information system

components which perform the functions of transformation, transmission, and storage.


Learning Objectives(continued)

• Explain the difference between essential and implementation descriptions of a system.

• Describe some of the major roles of information in a business organization.

• Explain the major steps in a problem-solving or decision-making process and how systems analysis can be understood as problem solving.


Overview

Systems analysis is a discipline which analyzes problems, estimates the consequences of various courses of action, and recommends what action to take to solve problems.

Information systems analysis seeks to improve information systems so that they provide better support for the business activities of an organization.


Overview (continued)

Humans cope with complexity by thinking in terms of systems. A system organizes its components into a structure and is separated from its environment by a system boundary.



System analysts work with abstract models in order to:

• Understand existing systems

• Simulate system behavior

• Describe the requirements for a new system



In general, information systems perform three functions:

• Transmission of information

• Storage of information

• Transformation of information



The important overall function of an information processing system is to respond to what happens in the outside world by transforming inputs into the desired outputs.



System analysts help solve business problems by applying information technology not only to production and service functions but also to improved monitoring, control, and decision support.


Coping with Complexity

In order to structure and simplify complexity, we:

• Limit the extent of our interest• Select only the important or essential

features• Break up the complexity into

manageable small pieces• Examine things iteratively• Review and refine in order to improve• Use visual thinking whenever we can


What Is a System?

A system is an interrelated set of components which are viewed as a whole.

It has:• Components – its basic parts• Structure – how the components are

organized• Function – what the system does• Objectives – the human purposes

served by the system


System Structures

• Hierarchical (Tree) Each component is subordinate to exactly one

other component. Components can be nested.

• Matrix (Grid) Each component, or cell, is determined by a

combination of two or more factors.

• Network Nodes or points connected by arcs or links. Arcs may permit flows, as in a transportation or

telecommunication network.


Hierarchical System Structure

.

FI GURE 1.1


Matrix System Structure

.FI GURE 1.4


Network System Structure

.FI GURE 1.5


A System and Its Environment

A system has a boundary which separates it from its environment.

FI GURE 1.6


Interfaces

An interface describes an interaction or connection between a system and its environment, or between subsystems.

FI GURE 1.7


System Models

A system model is an abstract, selective system description used to:

• Understand the system• Study system behavior• Communicate our understanding

of the system to others


System Models (continued)

A representation of a model is a graphical or physical way of displaying the components and relationships in the model.


Generating a System Model

We generate a system model through:

• Aggregation: Assembling it out of a set of elementary components, or primitives, through synthesis – a

bottom-up process.

• Decomposition: Partitioning the whole into its constituent parts through analysis – a top-down process.


Functions of an Information

Processing System• Communication

Moves or transports information from place to place

• Storage Records and saves information

for future use• Transformation

Changes information content by deriving outputs from inputs using a known, defined procedure


Automated Information Processing Systems

• Hardware Data capture and display devices Processing units Memory (volatile and permanent) Channels for information flow

• Software Operating system and related software Communications software Application software


System Descriptions

• Implementation Descriptions Dependent on a specific implementation

or technology Sometimes called physical descriptions

• Essential Descriptions Independent of a specific implementation

or technology Sometimes called logical descriptions


System Descriptions (continued)

Implementation

Description

Non-essential

Shows form

Concrete

Implementation-dependent

Technology-dependent

Essential

Description

Essential

Shows content

Abstract

Implementation- independent

Technology- independent


A Systems View of Business

• Industrial or manufacturing businesses, which produce goods

• Service businesses, which do not produce goods


A Systems View of Business (continued)

.

FI GURE 1.13


A Systems View of Business (continued)

.

FI GURE 1.14


Roles of Information in Business

1. It helps carry out the production and service functions of the organization.

2. It measures and monitors the performance of these primary business functions and other supporting functions.

3. It helps the organization control its operations to meet performance targets.

4. It supports management decisions to improve the business by modifying the organization or changing its objectives.


The Problem-Solving Process

1. Identify the problem.

2. Generate possible solutions.

3. By applying constraints, eliminate proposals which do not solve the problem.

4. Evaluate the expected performance or behavior of each proposed solution.


The Problem-Solving Process (continued)

5. Using the criteria, compare the alternatives to select the best solution.

6. Plan how to implement the selected solution.

7. Implement the solution.

8. Evaluate the performance of the solution after its implementation.


Summary

System analysts apply information technology to business problems and systems in order to improve production and services as well as provide improved monitoring, control, and managerial decisions.

Basic systems concepts and models help analysts succeed in addressing the complexity of real-world systems.

Documents

© 2005 Prentice Hall1-1 Stumpf and Teague Object-Oriented Systems Analysis and Design with UML