Requirements Analysis 2. 1 Req. Capture - 2005b502.ppt © Copyright De Montfort University 2000 All...
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Transcript of 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
Requirements Analysis 2. 2 Req. Capture - 2005b502.ppt
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Lecture 2 - Learning Objectives Identify the problems associated with
Requirements Capture Consider various fact-finding
approaches
Requirements Analysis 2. 3 Req. Capture - 2005b502.ppt
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Requirements Change
Why do requirements change?
Requirements Analysis 2. 4 Req. Capture - 2005b502.ppt
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The impact of change
0102030405060708090
100
Definition Development Maintenance
Cost to change
1X1X1.5X - 1.5X - 6X6X
60X -60X -100X100X
Requirements Analysis 2. 5 Req. Capture - 2005b502.ppt
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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 Analysis 2. 6 Req. Capture - 2005b502.ppt
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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
Requirements Analysis 2. 7 Req. Capture - 2005b502.ppt
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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 Analysis 2. 8 Req. Capture - 2005b502.ppt
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Requirements in RUP
Requirements Analysis 2. 9 Req. Capture - 2005b502.ppt
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Fact-Finding Techniques
Remembering the techniques:– S . . . – Q . . . – I . . .– R . . .– O . . .
Not in order of importance, or sequence in the project
Requirements Analysis 2. 10 Req. Capture - 2005b502.ppt
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Interviewing
The most widely used traditional technique
Requirements Analysis 2. 11 Req. Capture - 2005b502.ppt
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Interviewing
Preparing for an interview
Time-consuming ½ day preparation for one hour interview
Requirements Analysis 2. 12 Req. Capture - 2005b502.ppt
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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
Requirements Analysis 2. 13 Req. Capture - 2005b502.ppt
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Interviewing
A context-free question is: Always appropriate.
Requirements Analysis 2. 14 Req. Capture - 2005b502.ppt
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Interviewing
Examples of context-free questions used to find actors:
Who is the customer?
Requirements Analysis 2. 15 Req. Capture - 2005b502.ppt
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Interviewing
Context-free questions that help understand business processes and requirements:
How do you take a customer order at the moment?
Requirements Analysis 2. 16 Req. Capture - 2005b502.ppt
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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?"
Requirements Analysis 2. 17 Req. Capture - 2005b502.ppt
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Interviewing
Conducting an interview Introduce … Permission … Stay within agreed time State objectives- keep them in mind Show respect Don’t dominate But control direction
Requirements Analysis 2. 18 Req. Capture - 2005b502.ppt
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Interviewing
Conducting an interview Be flexible Seek evidence… Open questions “Reflect back” Summarise Can you return later?
Requirements Analysis 2. 19 Req. Capture - 2005b502.ppt
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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
Requirements Analysis 2. 20 Req. Capture - 2005b502.ppt
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Sampling
Almost always used to support interviews– Adds– Can resolve– Identifies– Confirms– Identifies
Requirements Analysis 2. 21 Req. Capture - 2005b502.ppt
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Sampling
Range from- highly informal to… rigorous statistical investigation
- sample size chosen for significance
Informal: collecting used documents
Requirements Analysis 2. 22 Req. Capture - 2005b502.ppt
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Sampling
Formal Sampling need to understand statistical theory to
set up study and analyse data
In all cases, minimise disruption to users.
Requirements Analysis 2. 23 Req. Capture - 2005b502.ppt
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Research / Reading Particularly useful at start of
project
Requirements Analysis 2. 24 Req. Capture - 2005b502.ppt
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Observation
Less widely used– Observation can:
Requirements Analysis 2. 25 Req. Capture - 2005b502.ppt
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Questionnaires
Questionnaires useful where: Many people involved with system Geographically dispersed
Requirements Analysis 2. 26 Req. Capture - 2005b502.ppt
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Questionnaires
Also bear in mind:
Requirements Analysis 2. 27 Req. Capture - 2005b502.ppt
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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.
Requirements Analysis 2. 28 Req. Capture - 2005b502.ppt
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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