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Requirements Modelling

Systems Analysis & DesignAcademic Year 2008/9

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Lecture 7Lecture 7


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Lecture Objectives

The aims of this lecture are to define:

Systems analysis phase activities The need for user involvement in

requirements modelling Joint Application development and Rapid

Application Development. The Traditional approach Object Oriented approach


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Systems Analysis Activities

The systems analysis phase includes three main activities (illustrated on the next slide)

Requirements modelling

Data and process modelling

Consideration of development strategies


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(1) Systems Analysis Phase 1 –Requirements modeling

Requirements modelling begins the process


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Requirements modeling

To describe and identify the requirements of a new system we need to first gather the facts:

required inputs/required outputs Processes Performance Security


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Definitions: Outputs refer to electronic or printed

information produced by the system

Inputs refers to the necessary data that enters the system – either manually or in an automated manner

Processes refer to the logical rules that are applied to transform the data


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Definitions continued

Performance refers to system characteristics such as speed, volume, capacity, availability and reliability

Security refers to hardware, software and procedural controls that safeguard and protect a system and its data from both internal and external threats.


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(2) Data and Process modeling

Once the requirements are modelled then attention moves to modelling the data and processes

Diagram from Shelley et al


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Data and Process modelling

Data and process modeling continues the modeling process by representing graphically (or conceptually) data and processes.

There are various methods for doing this, which we will learn about in later lectures and through practical case studies.

Examples include Use case models, data flow diagrams, etc.


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(3)Development Strategies

This phase is concerned with software trends, acquisition and development alternatives for the new system

Diagram from Shelley et al


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Development strategies

“The development strategies phase, considers various development options and prepares for the transition to the Systems Design Phase of the SDLC” (paraphrased from Shelley et al p92)

Recap-the systems development life cycle was explained in Lecture 2


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Defining the ‘Deliverable’

System Requirements DocumentThis is an overall design for the new system

Project management is now needed to co-ordinate people, tasks,

timetables and budgets.


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Project Management explained

The system requirements document provides the ‘blueprint’ of what is needed for the new system.

The Project management team then decide upon the best methods to achieve these requirements.

There are a number of Methodologies from which to choose.


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Methodologies (and Options)

Also called Development strategies

During project planning, it is necessary to choose from a range of methods

Each methodology (development strategy) uses different techniques to achieve the objectives of the new system requirements.


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Activity time

Working in 3’s, you will be an A, B or a C:

Consider the 3 stages we have just examined:

1. Requirements modelling – A students2. Data and Process modelling – B students3. Development strategies – C students


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Activity time

Working in 3’s, you will be an A, B or a C:

Write one or two sentences to explain what your stage is and what the analyst needs to do at that stage.


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Feedback and closure

Now exchange your notes so that you all have 3 definitions (one for each stage)

This is also your opportunity to ask any questions or make any comments.

Please be brief – time is short.


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Methodology 1) Structured Analysis

Often called the ‘Traditional method’ and used extensively in the early days of IT development.

Known as Structured Systems Analysis and Design Methodology (SSADM)

This methodology treats processes and data as separate entities.

Techniques used include Data flow diagrams


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Alternatives to ‘Traditional’

“IT professionals now recognise that successful systems must be USER ORIENTED

Users need to be involved formally or informally at every stage of the system development


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Result: Team Oriented methods and techniques

“Top managers expect the IT Department to deliver the best possible information system at the lowest possible cost in the shortest possible time” (p93 Shelley et al)

To fulfill these expectations many IT managers have tried to increase user participation


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(2) Joint Application Development

Joint application development (JAD) is a popular fact finding technique that brings users into the development process as active participants.

P93 Shelley et al

Users have a vital stake in the information system and so should participate fully in the development process


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The JAD approach

The JAD approach is a team approach which involves a task force of users, managers and IT professionals. They work together to:

Gather information Discuss business needs Define the new system requirements


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Typical JAD session Agenda


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(3) Rapid Application DevelopmentCharacteristics

RAD is another team based technique.

It speeds up the information system development process

It produces not just the model (as in JAD) but a fully functioning new information system quickly.

RAD is a complete methodology with a 4 phase life cycle.


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The four phases of the RAD model

Notice the continuous interaction between user design and construction


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(4) Object Oriented Methodology

Object oriented analysis or O.O. combines data and the processes that act on the data into things called objects.

These objects represent things, transactions and events that affect the system


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Object Oriented methods

This module will introduce and explain O.O methodology.

Lecture 8 will focus on how CASE tools and Unified Modelling language can be part of Object Oriented analysis concepts.


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In conclusion

This lecture has given you the opportunity to:

Examine systems analysis phase activities recognise the need for different development

strategies (methodologies) Be introduced to Traditional methods, OO,

Joint Application development (JAD) and rapid application development (RAD)

Understand the need for User involvement in the requirements modeling process.


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Recommended reading

Chapter 3 – Requirements Modelling pages 92 -97

Systems Analysis & Design. Shelley Cashman and Rosenblatt 6th Edition

Thomson Course Technology 2006

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