requirements analysis 2. 1 req. capture - 2005b502.ppt © copyright de montfort university 2000 all...

Requirements Analysis 2. 1 Req. Capture - 2005b502.ppt

© Copyright De Montfort University 2000All Rights Reserved

INFO2005Requirements Analysis

Requirements Capture

Department of Information Systems



Lecture 2 - Learning Objectives Identify the problems associated with

Requirements Capture Consider various fact-finding

approaches



Requirements Change

Why do requirements change?



The impact of change

0102030405060708090

100

Definition Development Maintenance

Cost to change

1X1X1.5X - 1.5X - 6X6X

60X -60X -100X100X



Why things go wrong

Type of Failure Reason for Failure Comment

QualityProblems

ProductivityProblems

Wrong problem addressed

Wider influences are neglected

Analysis carried out incorrectly

Project undertaken for wrongreason

Users change their mind

External events change theenvironment

Implementation is not feasible

Poor project control

From Bennett et. al. (1999)



Requirements Capture

We will be considering requirements capture in the context of the Unified Process

All thetechniques may be used in conjunction with development method

The traditional techniques are known collectively as Fact-Finding Techniques



Rational Unified Process

“The Rational Unified Process is a Software Engineering Process. It provides a disciplined approach to assigning tasks and responsibilities within a development organization. Its goal is to ensure the production of high-quality software that meets the needs of its end users, within a predictable schedule and budget. The Rational Unified Process captures many of the best practices in modern software development in a form that can be tailorable for a wide range of projects and organizations.”

Rational Software Corportation - RUP v5.1.1



Requirements in RUP



Fact-Finding Techniques

Remembering the techniques:– S . . . – Q . . . – I . . .– R . . .– O . . .

Not in order of importance, or sequence in the project



Interviewing

The most widely used traditional technique



Interviewing

Preparing for an interview

Time-consuming ½ day preparation for one hour interview



Interviewing

“An effective, direct person-to-person interviewing technique requires that you have prepared a list of questions designed to gain an understanding of the real problems and potential solutions. To get as unbiased answers as possible, you need to make sure the questions you ask are context free. The context-free question is a high-level, abstract question that can be posed early in a project to obtain information about global properties of the user’s problem and potential solutions.”

Rational Unified Process V5.1



Interviewing

A context-free question is: Always appropriate.



Interviewing

Examples of context-free questions used to find actors:

Who is the customer?



Interviewing

Context-free questions that help understand business processes and requirements:

How do you take a customer order at the moment?



Interviewing

Examples of non-context-free questions are:

Leading questions: "You need a faster printer, don't you?"

Self answering questions: "Are fifty items about right?"



Interviewing

Conducting an interview Introduce … Permission … Stay within agreed time State objectives- keep them in mind Show respect Don’t dominate But control direction



Interviewing

Conducting an interview Be flexible Seek evidence… Open questions “Reflect back” Summarise Can you return later?



Interviewing

Ending the interview Can I ask more questions later? Would you be willing to participate in a

requirements review? Is there anything else I should be asking

you?

Post-interview Write up asap (1/2 day per interview) Verify facts



Sampling

Almost always used to support interviews– Adds– Can resolve– Identifies– Confirms– Identifies



Sampling

Range from- highly informal to… rigorous statistical investigation

- sample size chosen for significance

Informal: collecting used documents



Sampling

Formal Sampling need to understand statistical theory to

set up study and analyse data

In all cases, minimise disruption to users.



Research / Reading Particularly useful at start of

project



Observation

Less widely used– Observation can:



Questionnaires

Questionnaires useful where: Many people involved with system Geographically dispersed



Questionnaires

Also bear in mind:



Documenting Requirements

Requirements must be carefully documented

Analyst’s notes must be:– summarised – organised– filed

One way to do this is to use a CASE tool– We will be using the Rational CASE tools.



Summary

In this session we have learned about various fact finding techniques - use the acronym SQIRO to help remember them.

References: Rational Unified Process Bennett, S. et. al. “Object-Oriented Systems

Analysis & Design using UML” McGraw-Hill 1999 Ch5 pp96–121

requirements analysis 2. 1 req. capture - 2005b502.ppt © copyright de montfort university 2000 all...

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