Week 3

Question 1

Release cycle for user stories in XP?

Answer 1

• Select user stories for this release
• Break down stories to tasks
• Plan release
• Evaluate system
• Release software
• Develop/integrate/test software

(Repeat- cyclic)

Question 2

What is refactoring?

Answer 2

XP proposes constant code improvement to make changes easier when they have to be implemented.

Refactoring: improving structure without changing external behaviour.

Question 3

Bad smells?

Answer 3

Poor or misguided programming.
E.g. code duplication, long methods, large classes, complex conditionals, long parameter list, etc…

Question 4

Black box vs white box testing?

Answer 4

Black-box testing: tester examines the software without having access to the internal code or implementation details.

White-box testing: tester has access to internal code.

Question 5

What is a requirement?

Answer 5

High-level abstract statement of a service or a system constrained to a detailed mathematical functional specification.

Question 6

Requirements engineering?

Answer 6

The process of establishing the service as that a customer requires from a system and the constraints under which it operates and is developed.

Question 7

User requirements?

Answer 7

Statements in natural language plus diagrams of the services the system provides and its operational constraints. Written for customers.

Question 8

System requirements?

Answer 8

A structured document setting out detailed descriptions of the system’s functions, services and operational constraints.

Defines what should be implemented so may be part of a contract between client and contractor.

Question 9

System stakeholders?

Answer 9

Any person or org affected by the system in some way and so who has a legitimate interest.

Question 10

Stakeholder types?

Answer 10

• End users
• System managers
• System owners

Question 11

Requirements engineering process?

Answer 11

Requirements elicitation
Requirements analysis
Requirements validation
Requirements management

RE is an iterative activity where these processes are interleaved.

Question 12

Challenges in RE?

Answer 12

Getting the requirements correct:
- Becomes exponentially expensive to correct mistakes later on. Easier to fix problems in requirement specification.

Question 13

Requirements completeness and consistency?

Answer 13

Requirements should be both complete and consistent.

Completeness: they should include descriptions of all facilities required.

Consistency: there should be no conflicts or contradictions in the descriptions of the system facilities.

Question 14

Domain requirements?

Answer 14

Constraints on the system from the domain of operation.
E.g. database, user interface, distributed system.

Question 15

Functional requirements?

Answer 15

Describes functionality or system services.

Functional user requirements may be high-level statements.
Functional system requirements should describe the system services in detail.

Question 16

Non-functional requirements?

Answer 16

These define system properties and constraints.
E.g. reliability, response time and storage requirements.

May affect the overall architecture of a system rather than the individual components.

Question 17

Non-functional classifications

Answer 17

Product requirements
- requirements which specify that the delivered product must behave in a particular way (e.g. speed, reliability).

Organisational requirements
- requirements which are a consequence of organisational policies and procedures (e.g. process standards used, implementation requirements).

External requirements
- requirements which arise from factors which are external to the system and its development process (interoperability, legislation).

Question 18

Requirements elicitation?

Answer 18

Software engineers work stakeholders to find out:
- About the application domain,
- The services that the system should provide,
- The performance of the system,
- Hardware constrains,
- etc…

1. Requirements discovery (gathering)
2. Requirements classification and organisation
3. Requirements prioritisation and negotiation
4. Requirements specification
   (Repeats- cyclic)

Question 19

Problems of requirements elicitation?

Answer 19

Stakeholders don’t know what they really want.

Different stakeholders may have conflicting requirements.

Organisational and political factors may influence the system requirements.

The requirements change during the analysis process.

Question 20

Requirements gathering technique: Individual interviews?

Answer 20

Formal or informal interviews with stakeholders are part of most RE processes.

Closed-ended question: based on pre-determined list.
Open-ended question: various issues are explored with stakeholders.

Benefits:
- Privacy
- Possibility to obtain in-depth stakeholder views

Cons:
- Time consuming
- Not good for understanding domain requirements

Question 21

Requirements gathering technique: Focus groups?

Answer 21

Aka group discussions / interviews

Facilitated by a moderator
Getting people to think about, discuss an issue or set of issues.

Benefits:
- uncover richer set of requirements in shorter periods
- natural peer interactions

Cons:
- dominant speakers
- peer pressure
- success depends on the moderator skills

Question 22

Requirements gathering techniques: Scenarios?

Answer 22

People usually find it easier to relate to real-life examples.

REs can use information gained from this discussion to formulate the actual system requirements.

Question 23

Requirements gathering techniques: Ethnographic studies?

Answer 23

Observational study:
- to understand the people behaviours and their cultures.
- requirements that are derived from the way that people actually work rather than the way which process definitions suggest that they ought to work,

Effective for understanding existing processes.

Question 24

Guidelines for writing requirements?

Answer 24

• Invent a standard format and use it for all requirements and be consistent.
• Use text highlighting to identify key parts.
• Avoid use of jargon.
• Include an explanation of why a requirement is necessary.

Question 25

Problems with using natural language for requirements specification?

Answer 25

Lack of clarity

Requirements confusion (functional and non-functional tend to be mixed up)

Requirements amalgamation (several different requirements may be expressed together)

Question 26

Requirements vs design?

Answer 26

Requirements should state what the system should do;
Design should describe how it does this.

These are inseparable.