Good Practices of Requirements Eng.Good Practices of Requirements Eng.

Copyright, 2000 © Jerzy R. Nawrocki

Jerzy.Nawrocki@put.poznan.pl

www.cs.put.poznan.pl/jnawrocki/mse/require/

Requirements Engineering Requirements Engineering

Lecture 1Lecture 100

Requirements Engineering Requirements Engineering

Lecture 1Lecture 100

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Plan of the lecturePlan of the lecturePlan of the lecturePlan of the lecture

IntroductionBasic guidelinesIntermediate guidelinesAdvanced guidelines

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Overview of RE guidelinesOverview of RE guidelinesOverview of RE guidelinesOverview of RE guidelines

The requirements document

Requirements elicitation

Reqs analysis & negotiation

Describing requirements

System modelling

Requirements validation

Requirements management

RE for critical systems

Basic Interm Adv

8

6

54

3

4

4

2

36

-

6

21

3

3

3

3

21

-

1

1-

-

1

2

4

9

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ScoringScoringScoringScoring

3 - standardised: documented standard followed and checked as part of the quality management process;

2 - normal use: widely followed but not mandatory;

1 - discretionary use: used at discretion of project manager;

0 - never: never or very rarely used;

3

0

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Maturity levels for REMaturity levels for REMaturity levels for REMaturity levels for RE

Defined

> 85 Basic & > 40 Interm & Adv

Defined

> 85 Basic & > 40 Interm & AdvRepeatable

> 55 Basic & < 40 Interm & Adv

Repeatable

> 55 Basic & < 40 Interm & AdvInitial

< 55 Basic

Initial

< 55 Basic

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Legend for RE quidelinesLegend for RE quidelinesLegend for RE quidelinesLegend for RE quidelines

• Responsibility of Project Managers• Responsibility of SDS Senior Responsibility of SDS Senior

Managers or Quality AssurersManagers or Quality Assurers• At a discretion of Project

Managers

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Plan of the lecturePlan of the lecturePlan of the lecturePlan of the lecture

Introduction

Basic guidelinesIntermediate guidelinesAdvanced guidelines

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Basic guidelinesBasic guidelinesBasic guidelinesBasic guidelines

Requirements document

• Define a standard document structureDefine a standard document structure• Explain how to use the document• Include a summary of the requirements

(purpose of the system, main actors, titles of main use cases)

• Make a business case for the system (usage scenarios: problem descriptions & improvement proposals)

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Basic guidelinesBasic guidelinesBasic guidelinesBasic guidelines

Requirements document

• Define specialised terms (glossary)• Lay out the document for readability• Help readers find information (?)• Make the document easy to change

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Basic guidelinesBasic guidelinesBasic guidelinesBasic guidelines

Requirements elicitation

• Assess system feasibility• Be sensitive to organisational &

political considerations• Identify and consult stakeholders• Record requirement sources• Define operating environment• Use business concerns to drive

requirements elicitation (planning game)

Give me a crocodile!

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Basic guidelinesBasic guidelinesBasic guidelinesBasic guidelines

Analysis and negotiation

• Define system boundaries (use case diagrams; interaction diagrams)

• Use checklists for requirements analysisUse checklists for requirements analysis (reading scenarios?)

• Provide software to support negotiationsProvide software to support negotiations (e-mail, ClearQuest)

• Plan for conflicts and conflict resolution (FAST & inspections)

• Prioritise requirements (planning game)

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Basic guidelinesBasic guidelinesBasic guidelinesBasic guidelines

Describing requirements

• Define standard templates for Define standard templates for describing requirementsdescribing requirements

• Use language simply & concisely• Use diagrams appropriately• Supplement natural language with

other descriptions of requirements (UML diagrams)

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Basic guidelinesBasic guidelinesBasic guidelinesBasic guidelines

System modelling

• Develop complementary system models (UML diagrams)

• Model the system’s environment• Model the system architecture

(deployment diagrams)

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Basic guidelinesBasic guidelinesBasic guidelinesBasic guidelines

Requirements validation

• Check that the requirements Check that the requirements document meets your standarddocument meets your standard

• Organise formal requirements Organise formal requirements inspectionsinspections

• Use multidisciplinary teams to Use multidisciplinary teams to review requirementsreview requirements

• Define validation checklistsDefine validation checklists

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Basic guidelinesBasic guidelinesBasic guidelinesBasic guidelines

Requirements management

• Uniquely identify each requirement

• Define policies for requirements Define policies for requirements managementmanagement

• Define traceability policiesDefine traceability policies• Maintain a traceability manual

(RequisitePro)

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Basic guidelinesBasic guidelinesBasic guidelinesBasic guidelines

RE for critical systems

• Create safety requirements Create safety requirements checklistschecklists

• Involve external reviewers in the Involve external reviewers in the validation processvalidation process

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Plan of the lecturePlan of the lecturePlan of the lecturePlan of the lecture

IntroductionBasic guidelines

Intermediate guidelinesAdvanced guidelines

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Intermediate guidelinesIntermediate guidelinesIntermediate guidelinesIntermediate guidelines

Requirements elicitation

• Record requirements rationale• Use scenarios

Give me a crocodile!

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Intermediate guidelinesIntermediate guidelinesIntermediate guidelinesIntermediate guidelines

Analysis and negotiation

• Classify requirements using using a multidimensional approach

• Use interaction matrices to find conflicts and overlaps

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Intermediate guidelinesIntermediate guidelinesIntermediate guidelinesIntermediate guidelines

Describing requirements

• Specify requirements quantitatively

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Intermediate guidelinesIntermediate guidelinesIntermediate guidelinesIntermediate guidelines

System modelling

• Use structured methods for system modelling

• Use a data dictionary• Document the links between

stakeholder requirements and system models

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Intermediate guidelinesIntermediate guidelinesIntermediate guidelinesIntermediate guidelines

Requirements validation

• Use prototyping to animate requirements

• Write a draft user manual• Propose requirements test

cases

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Intermediate guidelinesIntermediate guidelinesIntermediate guidelinesIntermediate guidelines

Requirements management

• Use a database to manage requirements (RequisitePro)

• Define change management policies (ClearCase LT, ClearQuest)

• Identify global system requirements

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Intermediate guidelinesIntermediate guidelinesIntermediate guidelinesIntermediate guidelines

RE for critical systems

• Identify and analyse hazards• Derive safety requirements from

hazard analysis• Cross-check operational and

functional requirements against safety requirements

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Plan of the lecturePlan of the lecturePlan of the lecturePlan of the lecture

IntroductionBasic guidelinesIntermediate guidelines

Advanced guidelines

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Advanced guidelinesAdvanced guidelinesAdvanced guidelinesAdvanced guidelines

Requirements elicitation

• Reuse requirements

Give me a crocodile!

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Advanced guidelinesAdvanced guidelinesAdvanced guidelinesAdvanced guidelines

Analysis and negotiation

• Assess requirements risks (exploration & planning game)

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Advanced guidelinesAdvanced guidelinesAdvanced guidelinesAdvanced guidelines

Requirements validation

• Paraphrase system models

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Advanced guidelinesAdvanced guidelinesAdvanced guidelinesAdvanced guidelines

Requirements management

• Identify volatile requirements• Record rejected requirements

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Advanced guidelinesAdvanced guidelinesAdvanced guidelinesAdvanced guidelines

RE for critical systems

• Specify systems using formal specification

• Collect incident experience• Learn from incident experience• Establish an organisational

safety culture

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Further readingsFurther readingsFurther readingsFurther readings

• I. Sommerville, P. Sawyer, Requirements Engineering, John Wiley & Sons, Chichester, 1997.

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Quality assessmentQuality assessmentQuality assessmentQuality assessment

1. What is your general impression? (1 - 6)

2. Was it too slow or too fast?

3. What important did you learn during the lecture?

4. What to improve and how?