1. Requirements Engineering Lecture 2
Jerzy Nawrocki
Requirements Engineering
Lecture 2
Usage Scenarios
Copyright, 2000 © Jerzy R. Nawrocki
Requirements Eng., Lecture 2

2. J. Nawrocki, Requirements Eng., Lecture 2
Jerzy Nawrocki
Plan of the lecture
Introduction
Document structure
Verification checklist
Process description
Measurements
J. Nawrocki, Requirements Eng., Lecture 2
Requirements Eng., Lecture 2

3. J. Nawrocki, Requirements Eng., Lecture 2
Jerzy Nawrocki
Introduction
Binary
I mean
1 + 1 ?
‘Scenarios are examples of interaction sessions which are concerned with a single type of interaction between an end-user and the system.’
is 10
System
End-user
J. Nawrocki, Requirements Eng., Lecture 2
Requirements Eng., Lecture 2

4. J. Nawrocki, Requirements Eng., Lecture 2
Introduction
Scenario contents (Sommervill):
initial state of the system
normal flow of events
exceptions
concurrent activities
final state of the system
scenario
J. Nawrocki, Requirements Eng., Lecture 2

5. J. Nawrocki, Requirements Eng., Lecture 2
Jerzy Nawrocki
Document structure
Concept of the system
1 Introduction
1.1 Purpose of the document
1.2 Viewpoints and stakeholders
1.3 Brief description of the system
1.4 Business case for the system
1.5 Definitions, acronyms and abbreviations
1.6 References
1.6 Overview of the remainder of the document
J. Nawrocki, Requirements Eng., Lecture 2
Requirements Eng., Lecture 2

6. Concept of the system (contd.)
Jerzy Nawrocki
Document structure
Concept of the system (contd.)
2 Usage scenarios
2.1 Scenario P1: Printing a file
2.1.1 Actor(s)
John is ...
2.1.2 Goal
John wants to ...
2.1.3 Behaviours description
J. Nawrocki, Requirements Eng., Lecture 2
Requirements Eng., Lecture 2

7. Concept of the system (contd.)
Jerzy Nawrocki
Document structure
Concept of the system (contd.)
2.1.3 Behaviours description
Behaviour B1: Normal
Start state
Flow of data and events
Final state
Behaviour B2: LP does not work
J. Nawrocki, Requirements Eng., Lecture 2
Requirements Eng., Lecture 2

8. Concept of the system (contd.)
Jerzy Nawrocki
Document structure
Concept of the system (contd.)
2.1.4 Rationale / Contribution to the
organisation’s goals
2.1.5 Possible problems
2.1.6 Source(s) of the scenario
3. Non-functional requirements
4. Risk factors & system feasibility
5. Workload for scenarios elicitation
5.1 Planned
5.2 Actual
J. Nawrocki, Requirements Eng., Lecture 2
Requirements Eng., Lecture 2

9. Concept of the system (contd.)
Jerzy Nawrocki
Document structure
Concept of the system (contd.)
6 Change requests
6.1 Accepted
6.2 Rejected
7. Questionnaire for reviewers
Appendix: Rejected scenarios
J. Nawrocki, Requirements Eng., Lecture 2
Requirements Eng., Lecture 2

10. Verification checklist
Does the document follow the standard document structure?
Is the list of viewpoints complete?
Is the list of viewpoints clearly described?
Is the list of stakeholders complete?
Are the stakeholders clearly described (one needs at least: role description, name of the person, , phone/address)?
J. Nawrocki, Requirements Eng., Lecture 2

11. Verification checklist
Is the brief description of the system clear and complete?
Is the business case for the system clearly and completely described?
Are all the terms and abbreviations explained?
Is that explanation clear?
Is the list of references complete?
Is each reference completely described?
Are the referenced items available for the team?
J. Nawrocki, Requirements Eng., Lecture 2

12. Verification checklist
Is the overview of the remainder of the document clear, complete, and not too lengthy?
Is each scenario important from the business perspective?
Is it technically feasible to implement each scenario?
Is each scenario clearly described?
Is the set of behaviours complete?
Is the rationale for each scenario convincing?
J. Nawrocki, Requirements Eng., Lecture 2

13. Verification checklist
Is the list of possible problems complete?
Are the possible problems clearly described?
Are the sources of scenarios well documented?
Are the non-functional requirements clearly stated?
Does the list of non-functional requirements contain the project deadline / duedate?
Are any important and probable risk factors missing on the list?
J. Nawrocki, Requirements Eng., Lecture 2

14. Verification checklist
Is the workload information well documented?
Are change requests well documented?
J. Nawrocki, Requirements Eng., Lecture 2

15. J. Nawrocki, Requirements Eng., Lecture 2
Process description
Week schedule
A. Initial / next version of the document
Wednesday 13:00 - Monday 10:00
 Sending the document out by Monday 10:00
B. Individual preparation to the meeting
Monday 11:00 - Tuesday 14:00
C. Internal/formal review meeting (Tu 15:00|16:30)
D. Writing the meeting minutes
Tuesday 18:00 - Wednesday 12:00
 Sending the minutes out by Wednesday 12:00
J. Nawrocki, Requirements Eng., Lecture 2

16. The usage scenario phase
Process description
The usage scenario phase
1. Initial version ( ) ~ 4 scenarios
2. Second version ( ) ~ 10 scenarios
3. Third version ( ) ~ 10 scenarios
4. Formal review ( )
 Sending the document out by 3.11, Fri, 10:00
5. Follow-up & document freezing ( )
J. Nawrocki, Requirements Eng., Lecture 2

17. Early phases in SDS projects
Process description
Early phases in SDS projects
1. Initial Project Description
2. Usage scenarios
3. Software Requirements Specification
4. Software Plan
J. Nawrocki, Requirements Eng., Lecture 2

18. J. Nawrocki, Requirements Eng., Lecture 2
Measurements
Time spent on ..
A. Initial / next version of the document
B. Individual preparation to the meeting
C. Internal/formal review meeting
D. Writing the meeting minutes
J. Nawrocki, Requirements Eng., Lecture 2

19. J. Nawrocki, Requirements Eng., Lecture 2
Measurements
Time spent on ..
Doc - writing a version of the document
Prep - preparation to the meeting
Meet - internal/formal review meeting
Min - writing the meeting minutes
J. Kowalski, Project: Gtest, Phase: Scenarios, Week: 2
J. Nawrocki, Requirements Eng., Lecture 2

20. J. Nawrocki, Requirements Eng., Lecture 2
Measurements
Delays in ..
Better late than
never!
 Sending the document out by Monday 10:00
C. Starting internal/formal review meeting
 Sending the minutes out by Wednesday 12:00
J. Nawrocki, Requirements Eng., Lecture 2

21. J. Nawrocki, Requirements Eng., Lecture 2
Measurements
Delays in ..
Area manager: B. Walter, Project: GTest
J. Nawrocki, Requirements Eng., Lecture 2

22. J. Nawrocki, Requirements Eng., Lecture 2
Measurements
Performance
J. Kowalski & A. Nowak, Project: GTest
J. Nawrocki, Requirements Eng., Lecture 2

23. J. Nawrocki, Requirements Eng., Lecture 2
Measurements
Defects
Nothing is
perfect!
Verification checklist (report)
J. Nawrocki, Requirements Eng., Lecture 2

24. J. Nawrocki, Requirements Eng., Lecture 2
Summary
Verification procedure is based on the document structure
Process definition has two levels:
week level
phase level
Measurement is based on both the document structure and the process definition
At last!
J. Nawrocki, Requirements Eng., Lecture 2

25. J. Nawrocki, Requirements Eng., Lecture 2
Jerzy Nawrocki
Further readings
I. Sommerville, P. Sawyer, Requirements Engineering, John Wiley & Sons, Chichester, 1997. 
J. Nawrocki, Requirements Eng., Lecture 2
Requirements Eng., Lecture 2

26. J. Nawrocki, Requirements Eng., Lecture 2
Jerzy Nawrocki
Homework
Write a document ‘Concept of the system’ containing at least one scenario with two different behaviours.
J. Nawrocki, Requirements Eng., Lecture 2
Requirements Eng., Lecture 2

27. J. Nawrocki, Requirements Eng., Lecture 2
Quality 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?
J. Nawrocki, Requirements Eng., Lecture 2