Introduction to System Analysis and Design

- Dr. Mahmoud Abu-Arra

- Mr. Ahmad Al-Ghoul

System Analysis and Design

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Learning Objectives

Explain systems development tools, including modeling, prototyping, and CASE tools

Discuss and distinguish between system development methodologies

Explain systems development methods, RAD, JAD

Distinguish between structured analysis and object-oriented methodology

Discuss how to use appropriate system development method

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Introduction

There are several tools and techniques to build information systems, to choose the appropriate one to build your system, you must study them first and knows their uses.

Methodology is an approach, a method or a technique for developing information systems. The methodology defines a method and a way of developing an information system, guiding planners in the desired working method.

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Systems Development Tools and Techniques

Systems analysts must know how to use a variety of techniques such as modeling, prototyping, and computer-aided systems engineering tools to plan, design, and implement information systems.

Systems analysts work with these tools in a team environment, where input from users, managers, and IT staff contributes to the system design.

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Systems Development Tools and Techniques

Modeling Modeling produces a graphical representation of a concept or

process that system developers can analyze, test, and modify. Modeling Used to describe and simplify an information system:

Business model or Requirements model Describes the information that a system must provide.

Data model Describes the data structure and design.

Object model Describes objects, which combine data and processes.

Network model Describes the design and protocols of telecommunication links

Process model Describes the logic that programmers use to write code modules

Modeling techniques, including data flow diagrams and entity relationship diagrams, and unified modeling language diagrams.

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Systems Development Tools and Techniques

Pros Speeds up the development

process significantly

Users interact with Prototype very quickly

Users can identify needed changes and refine real requirements

Cons Important decisions might be

made too early, before business or IT issues are thoroughly understood

Initial Design decisions may be poor

Prototyping

Prototyping tests system concepts and provide an

opportunity to examine input, output, and user

interface before final decisions are made.

Early working version of an information system

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Systems Development Tools and Techniques

Computer-Aided Systems Engineering (CASE) Tools Also called computer-aided software

engineering, is a technique that uses powerful software, called CASE tools, to help systems analysts develop and maintain information systems.

Framework for systems development and support a wide variety of design methodologies

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Methodologies in the development of information systems

Bottom up A formalized approach to implementing the SDLC

A series of steps and deliverables

As the base for the information system, this approach uses the organization’s operational level.

The starting point is that, the operational level constitutes the core of the organization.

The information requirements of the intermediate and management levels will be supplied by the various processing stages of operational level data.

Using this approach, studying the needs and planning of the future system will be prepared initially for the operational level.

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Methodologies in the development of information systems

Top Down This approach uses the organization’s management level as the base for the information system. The definition of its requirements and the system goals are dictated by the organization’s management.

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Methodologies in the development of information systems

Integrated Approach

This approach combines both methods, with the aim of benefiting from both the Bottom Up and the Top Down approaches.

With this approach, the initial planning is carried out by the Top Down method

The planning of the systems themselves (sub-systems) is performed using the Bottom Up approach in order to ensure proper planning, based on operational level requirements.

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Methodologies in the development of information systems

Structured Analysis “Structured analysis is a set of techniques and graphical tools that

allow the analyst to develop a new kind of system specification that are easily understandable to the user. Analysts work primarily with their wits, pencil and paper.” [Kendall 1996]

Uses a set of process models to describe a system graphically

The availability of CASE tools in the 1990s enabled analysts to develop and modify the graphical SASD models.

[1]

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Methodologies in the development of information systems

Object-oriented (O-O) analysis O-O analysis combines data & processes into things

called objects

O-O analysis uses object models to represent data and behavior, and to show how objects affect other objects

By describing the objects (data) and methods (processes) needed to support business operation, a system developer can design reusable components that allow faster system implementation and decreased development cost

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Methodologies in the development of information systems

Object-oriented (O-O) analysis objects combine data and processes. Object are the end

product of object-oriented analysis. Object is a member of a class

Class is a collection of similar objects Objects possess characteristics called properties Properties inherits from the object class or possesses on its own In O-O design, built-in processes called methods can change an

object’s properties Object can send information to anther object by using a

message A message requests specific behavior or information from

another object

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Methodologies in the development of information systems

The PERSON class includes INSTRUCTOR and STUDENT objects, which have their own properties and inherited properties.

Object-oriented (O-O) analysis

[1]

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Methodologies in the development of information systems

Joint Application Development and Rapid

Application Development

JAD – The basic idea behind JAD is to bring structure to the requirements determination phase of analysis and to the reviews that occur as a part of design.

Team based fact finding

Users, Managers and Analysts work together for several days

System requirements are reviewed

Structured meetings

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Methodologies in the development of information systems

RAD – created to radically decrease the time needed to design and implement information systems.

RAD relies on extensive user involvement.

Incorporate special techniques and tools:

CASE tools

JAD sessions

Fourth generation/visualization programming languages

Code generators

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Methodologies in the development of information systems

There are many other methods A systems analyst should

understand the alternative methodologies and their individual strengths and weaknesses.

how you will choose the suitable method?

Selecting a methodology is not simple, as no one methodology is always best.

Many organizations have their own standards.

We will discuss this topic in more detail in the analysis chapter

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Sequence Summary

In this Sequence we have

Discussed the various systems development methods, tools, and techniques

Distinguished between structured analysis and object-oriented methodology

Discussed how to use appropriate system development method

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Reference

[1] System Analysis and Design, Sixth Edition Authors: Gary B. Shelly, Thomas J. Cashman and Harry J. Rosenblatt , Publisher: SHELLY CASHMAN SEWIES. [2] Modern Systems Analysis and Design Third Edition Authors: Jeffrey A. Hoffer , Joey F. George, Joseph S. Valacich Publisher: prentice hall [3] System Analysis and Design, 3rd Edition Authors: Dennis, Wixom, & Roth Publisher: John Wiley & sons