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Requirements Elicitation


Requirement techniques

Presentation based on courses given at SEI Carnegie Mellon (USA) and Kingston Univ (GB)

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Presentation based on courses given at SEI Carnegie Mellon (USA) and Kingston Univ (GB)

Case Studies

Standards

Projects

Req. Validation

Exchanging Req.

Req. Expression &

Modelling

System engineering

Req. Management

Req. Elicitation

Basic introduction

RE Techniques

Requirement Engineering

Req. Traceability

Software systems

Reactive systems

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Contents

Requirements elicitation

Guidelines

Methodology

Basic techniques for eliciting requirements

Interviews

Meetings

Planning...

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Some basic points

Elicitation is not Acquisition

Requirements are not available like sensor data

Notjust read them systematical ly ! !

Elicitation is not specification and modelling

Too much importance has been given toexpression and modelling

RE Determines the successof the mission

Elicitation detrmines the successof the REprocess

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What Is Elicitation ?

Process of identifying needs

Front End to systems development

Involves social, communicative issues and

Technical issues

Requirement expression is the step to model

the requirements.

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A common Problem !!

What is your need ?

I need a system that

works OK

Robust and respond tomy wishes

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As problems in social life

AVOID M ISUNDERSTANDI NG !!
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A simple scenario

I need a book

What for ? Or What discipline ?

To .....; in fact anything to level up my terminal

So you any item but Not necessarily a book
http://www2.freeze.com/cgi-bin/imageFolio.cgi?direct=Clip_Art/Business/Computers&img=

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Elicitation : a subset of goals

Identify the relavant parties . The stackholders

Gather the Wish Listfor each stachholder

Document and refine the Wish list

Expected properties

Unambiguous Complete

Verifiable

Consistent Modifiable

Traceable

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Common generic problems

Scope : too much or too littleUnderstandings : Users and developpers

Users have an incomplete understanding of their

needs

Analysts and SE have a poor knowledge of

problem domain

Ease of omitting obvious information Volatility :changing requirements

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The Scope problem

Establish a bounday conditions for the target system

Organisation and context analysis
http://www2.freeze.com/cgi-bin/imageFolio.cgi?direct=Clip_Art/Animals/Birds&img=56

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The Misunderstanding pb
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Some data on the Pb

56 % of errors were due to poor communication

between user and analyste

Such errors cost 82% of the available staff time

Three main issuespeople involved comes from different backgrounds

Language used may be too informal or too formal

A large amount of information to be commnicated

and not really structured

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The misun ...

Stakholders may be located at different levels

May correspond to levels to abstraction

From informal knowledge to ...formal

expression

Notion of maturity levels

Dont mix up with abstraction levels

Many people are involved : Questions When in the eliciaition process ?

At what level ?

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The Volatility problem

REQUIREMENTS EVOLVE : A basis

Some requiremenrs are more emphasized than needed

during elecitation process

The boss is always rightsHis needs are more considered even not mature and

ambigous

Change may occur due to

Misunderstanding

Scope

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An Elicitation methodology Framework (DOD-SEI)

basic remark : Most requirements problems are due to

requirements elicitation

General remark . No technique is comprehensive

enough to adequatly cover all mentionned issues

Objective : Synthesize all methods and techniques

into a methodology which can be instantiated upon a

target systems atributes

bl i d

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See table 4.1 in SEI document

Information gathering

Requirements Expression and analysis (see

later course on this topic)

Validation

h li i i h d l

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The Elicitation methodology

Fact findings

Req Gathering

Evaluation

Prioritisation

Integration

and Validation

F fi di

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Fact findingsUser Developper

Identify Stackholders

Determine operational and

problem contexte

Identify other systemsPerform context analysis

Identify domain experts

Id. Domain

Conduct technological

surveyAsses cost/implementation

R i h i

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Requirements gatheringUser Developper

Get Wish List Classify wish list

* Functional

* NFR

* Env.

* ...

See www.incose.org/rwg

paper on requirementscategrorisation

E l i d i li i
http://www.incose.org/rwghttp://www.incose.org/rwg

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Evaluation and rationalisationUser Developper

Perform abstraction to

answer question

see interview

techniques

Perform risk assessment

Cost benefit ...

P i i i i

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PrioritisationUser Developper

* Dtermine criticality Prioritisation of requirements

basis : cost, criticality, ...

I i d lid i

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Integration and validationUser Developper

Adress completeness :TBD type

validate req with respect

concept of operation

Decide to go on next step

* Demo

* prototype

* ...

Consistency checking

C l i th th d l

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Conclusion on the methodology

Abstract methodology

Still be considered as guide

An evaluation crireria to be developped :

No information on evaluation

Th t kh ld ti

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The stackholder connection

Sometimes called requirements analysis or

requirements discovery Involves technical staff working with

customers to find out about the applicationdomain, the services that the system shouldprovide and the systems operationalconstraints

May involve end-users, managers, engineers

involved in maintenance, domain experts,trade unions, etc. These are calledstakeholders

S ifi li it ti t h i

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Specific elicitation techniques

Documentation

Interviews

Questionnaires

Scenarios

Ethnography

G h i I f i Ab

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Gathering Information About...

The organisation

goals, structure, functional units, policies The people

authority, duties, relationships, information,

needs The work

tasks, work flows, procedures, schedules,

volumes, performance criteria The work environment

work areas, resources

G th i I f ti F

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Gathering Information From...

Documentation charts, manuals, job descriptions, forms,

reports

System users and managers External sources

other companies, vendors, publications,

seminars, workshops, on-line data services

I t i

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Interviews

The requirements engineer or analyst

discusses the system with differentstakeholders and builds up an

understanding of their requirements.

Identify work flows

factors that influence the operations of systems

the elements (documents, procedures, policies etc.)that make up systems

T f I t i

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Types of Interviews

Closed interviews. The requirements

engineer looks for answers to a pre-definedset of questions

goal-directed and systematic

Open interviews There is no predefinedagenda and the requirements engineer

discusses, in an open-ended way, what

stakeholders want from the system. Appropriate when we want to explore an issue

establish rapport and obtain a broad view

I t i i ti l

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Interviewing essentials

Interviewers must be open-minded and

should not approach the interview with pre-conceived notions about what is required

Stakeholders must be given a starting point

for discussion. This can be a question, arequirements proposal or an existing system

Interviewers must be aware of

organisational politics - many realrequirements may not be discussed because

of their political implications

I t i St

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Interview Steps

Preparing

Planning

Opening and Closing

Conducting

Following up

Preparing for the interview

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Preparing for the interview

Review

organisation reports

annual reports

statements of departments goals

long-range planning goals

existing procedure manuals

systems documentation

understand their language

Planning of Interviews

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Planning of Interviews

Identify sources

prepare

* purpose, outline of points to cover

venue

appointments

prepare the interviewee

* points to cover, useful documents

Questioning

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Questioning

Open questions

tell me what happens when a customer calls

leading questions

be wary of negative responses

exceptions?

Subjects who try to please

Listening

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Listening

Judge content and not delivery

withhold evaluation and response

be flexible

work at listening

resist distractions

keep your mind open

listen for ideas

Opening and closing and Following Up the interview

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Opening and closing and Following Up the interview

Introduce yourself

state the purpose of the interview

briefly summarise the areas that have been

discussed, highlight important points and

your understanding of them

thank the interviewee for the time

Ask closed questions

Document the results

Questionnaires

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Questionnaires

Validity

- sample size, audience

Reliability

Questions

- open ended

- fill in the blank

- multiple choice- rating scales

Scenarios

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Scenarios

Scenarios are stories which explain how a

system might be used. They should include

- a description of the system state before

entering the scenario

- the normal flow of events in the scenario

- exceptions to the normal flow of events

- information about concurrent activities

- a description of the system state at the end of

the scenario

Scenarios

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Scenarios

Scenarios are examples of interactionsessions which describe how a user interacts

with a system

Discovering scenarios exposes possiblesystem interactions and reveals system

facilities which may be required

Operational semantics

Observation and social analysis

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Observation and social analysis

People often find it hard to describe what

they do because it is so natural to them.

Sometimes, the best way to understand it is to

observe them at work

Ethnography is a technique from the social

sciences which has proved to be valuable in

understanding actual work processes

Actual work processes often differfromformal, prescribed processes

Meetings

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Meetings

Meetings consume resources

must improve quality of meetings

Meetings have different objectives

solve problems, clarify issues

brainstorm solutions to problems resolve conflicts

conduct reviews

collect and merge facts and data report progress

assign actions

Meetings: Planning

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Meetings: Planning

Define clearly the expected results or

outcomes of the meeting

Find if possible a way to eliminate the needfor the meeting

do we really need the outcome of this meeting atthis moment?

Is there another more efficient and more effectiveway to accomplish what is to be accomplished by

holding this meeting? If yes and no are the answers to the two questions

then proceed

Meetings: Planning

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Meetings: Planning

Prepare agenda for the meeting

reasonable time allocation for each topic circulate at least two days before the meeting

to allow time for the attendees to prepare, comment and makeschedule arrangements

identify and notify required meeting attendees. Must have theright people

the appropriate information and knowledge to support meetinggoals and objectives

the authority )direct or delegated) to make decisions and

commitments if required by the meetings goals and objectives

the need to understand what is going on and the rationale behindany decisions or commitments made during the meeting

Meetings: Planning

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Meetings: Planning

Meeting location considerations

room size, lighting, noise, temperature, humidity candistract

need for audio/visual aids in working order

Start and Finish on time

Record and publish minutes

Have handouts ready for distribution

review the agenda, meeting goals and objectivesfirst

discourage interruptions and deflections from thetopic at hand

follow the agenda schedule as closely as possible

Active Listener Guidelines

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Clear your mind of everything except the speaker,

the topic and what the speaker is actually saying.Prevent trying to read more into what the speakeris saying than the speaker is actually saying

Capture as accurately as possible the information

that the speaker is conveying Let the speaker know by actions that s/he is

interested in what is being said

Ask questions as they arise to clarify points,indicate understanding and provide feedback tothe speaker


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Ask that the central ideas, themes and summaries

be repeated to assure complete understanding

Do not attempt to formulate replies, rebuttals or

counterexamples while the speaker is talking

Do not draw conclusions until you have heard thewhole story

Accept that understanding is not agreeing

Do not be afraid to ask if there is something that

you have not been told.

Methodologies

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Methodologies

A number of techniques are available todescribe the workings of a system

Many people have taken a number of these

techniques and produced a method for usingthem to arrive at a specification

Methodologies Division

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Methodologies Division

Main Division

Data driven

SSADM

Process driven

Yourdon JSD

Is there a universally best methodology?

No

Can I combine methodologies?

Maybe

Comparison of Methodologies

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Comparison of Methodologies

Can one compare the available methodologies?

against an ideal methodology

not feasible because no suitable specification of an ideal

methodology exists

assess the features and facilities of each methodology within

a formalised framework

invent questions about each methodology

ask the questions for each methodology

merge and describe the results

decide?

Typical Comparison Questions

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Typical Comparison Questions

For the comparison one may ask

Does the methodology cover all phases? Which ones? How

thoroughly.

Are the steps fairly proceduralised or does the methodology

only give broad directions? Are analysis, design and

implementation given equal weight?

Is it data or process analysis oriented?

Does it cover prototyping and incremental development?

How are the results of analysis and design expressed?

Is the methodology supported by software?

What types of applications is it suited to? History?

Decomposition Diagrams

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Decomposition Diagrams

A high-level organisation (or function or activity)

is decomposed into lower organisations (orfunctions or activities). The lower we go in the

hierarchy the greater the detail revealed

Used to show organisation, system, program, fileand report structures

organisation

functions

processes procedures

program structures

Viewpoints for requirements elicitation

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Viewpoints for requirements elicitation

The Preview approach adresses the cases

where

Sources from radical sources

Identify key business drivers

Incremental process for requirement elicitation

PREVIEW Components

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PREVIEW Components

Viewpoint name : an identifier

Viewpoint focus : interaction, domain, stakeholder

Viewpoint concerns : all concerns applicable

Viewpoint sources : individuals, documents

Viewpoint requirements : Req. from source

Viewpoint history : changes record

Limited only to requirement elicitationand NOT Validation

Example (Sommerville paper ICRE-98)

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Example (Sommerville paper ICRE 98)

Emergency braking system

Viewpoint name : emergency braking system

Viewpoint focus : The protection system of the train which mustdetect dangerous condistions and apply emergency braking to bring train to a

safe state

Viewpoint concerns : Safe compatibility

Viewpoint sources : systems design; function spec of existingprotection software

Example

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Example

Viewpoint requirements : 1. Detection of excess speed , ifthe speed of the train exceeds the safe speedfor the current track segment bymore than 6 kmh emergency braking must be applied

2. Detection of overshooting, if the signal sensor indicates a danger setting

and the front of the train has entered the signalled track segment,

emergency braking shall be applied3. Frequency of invocation , detection of excess speed, detection of

overshooting, and determining the necessity of emergency brake application

shall be performed once every iteration of the on board software

application cycle

Viewpoint history : case of evolving requirement(following anaccident or a failure)

Conclusions

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Conclusions

Elicitation Process is The FIRST PHASE

Needs to be successfulJust DO IT

Be convinced it needs to be done

Any technique will do (see resources and

papers)

Next lecture

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Next lecture

RequirementsManagement

Requirements elicitation

Reading and assignment

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Reading and assignment

Papers

Christel & Kang : Issues in requirement elicitation Read sections 1 through 6 of the paperIssues in Requirements Elicitationand answer the following questions:

1. Describe an example requirements elicitation for each of the three major categories of elicitation problems and suggest

a technique for solution.

2. What are the chief differences between the user-oriented and developer-oriented tasks of requirements elicitation?

Contact XX for requirement elicitation for thefollowing concept of operation

HPI Scheduler

Web site for RE course

A students utilities to be done at HPI (web site for students).
http://www.cs.cmu.edu/~SW_Managemnt/ps/tr12.92/TR-12-94.001.htmlhttp://www.cs.cmu.edu/~SW_Managemnt/ps/tr12.92/TR-12-94.001.html

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