1. Chapter 17 I.Omaima Al-Matrafi
Software Quality
Chapter 17
I.Omaima Al-Matrafi

2. Exercises
1. Briefly explain the five different views of software quality.
2. Briefly explain how one can measure the user’s view of software quality.
3. Briefly explain how one can measure the manufacturer’s view of software
quality.
4. Briefly explain McCall’s quality factors and quality criteria.
5. Briefly explain McCall’s categorization of quality factors into three quality
criteria.
6. Briefly explain the ISO 9126 quality characteristics.
7. Compare McCall’s quality model with the ISO 9126 quality model.
8. State some difficulties in applying the McCall and ISO 9126 quality models.
9. Briefly explain the ISO 9000:2000 (Fundamental) document for quality assurance.
10. Briefly explain the ISO 9001:2000 (Requirements) document for quality assurance.

3. 1. Briefly explain the five different views of software quality.

4. The five views of software quality are
Transcendental view, SQ is something that can be perceived through experience alone. A good quality object clearly stands out.
The user view of quality concerns the extent to which user needs and expectations have been fulfilled.
In the manufacturing view, quality is something conforming to requirements. The concept of a process plays a key role in manufacturing. Products must be manufactured by following process standards.
In the product view,. The central idea in the product view is internal qualities are thought to affect external qualities.
Value based view is how much a customer is willing to pay for a certain level of quality. (tradeoff between quality and cost).

5. 2. Briefly explain how one can measure the user’s view of software quality.

6. To measure the user view of SQ
Identify the external quality attributes of a system.
Examples: functionality, Usability and reliabilty.
Functionality : can be computed as the ratio of the number of pass test cases to the total number of test cases.
Reliability : measured by counting the number of faults or the failure rate of a system.
OR apply Gilb’s technique :broken down into component parts until each can be stated in terms of directly measurable attributes

7. 3. Briefly explain how one can measure the manufacturer’s view of software quality.

8. Manufacturers count two things as a measure of SQ
Defect count: The total number of defects detected during development and operation.
It is a measure of the quality of the work produced.
Rework cost: that is how much it costs to fix the defects.
pre-release (development) rework cost: is a measure of development efficiency
post-release (oparation) rework cost: is a measure of delivered quality.

9. 4. Briefly explain McCall’s quality factors and quality criteria.
A quality factor: represents a behavioral characteristic of a system. McCall’s 11 quality factors are:
correctness, reliability, efficiency, integrity, usability, maintainability, testability, flexibility, portability, reusability, and interoperability.
A quality Criterion: is an attribute of a quality factor that is related to software development. McCall suggested 23 quality criteria.
Ex: modularity  maintainability

10. 5. Briefly explain McCall’s categorization of quality factors into three quality criteria.

11. McCall’s quality factors relate more to the quality of delivered products, rather than products in development or development processes themselves.

12. 6. Briefly explain the ISO 9126 quality characteristics

13. 7. Compare McCall’s quality model with the ISO 9126 quality model.
ISO 9126 model
(quality characteristic)
McCall model
(quality factor)
High-level factors/characteristics in both models are:
reliability, usability, efficiency, maintainability, and portability.
Similarity
External characteristic
(visible to user)
Internal characteristic
Differences
1 Q subcharacteristic impact 1 Q characteristic
1 Q attribute can impact several Q factors
Testability: is a low level (subcharacteristic) of maintainability
Testability : is a high level factor

14. 8. State some difficulties in applying the McCall and ISO 9126 quality models.
No consensus about what high level quality factors are important. (McCall 11,ISO 6)
No consensus about what is a top level quality characteristic and what is a more concrete quality sub- characteristic (or attribute). Interoperability.
An absence of rationale in both the quality models. Hence, it is difficult to follow a prescribed model

15. 9. Briefly explain the ISO 9000:2000 (Fundamental) document for quality assurance.
This is based on eight principles.
Customer focus
Leadership
Involvement of people
Process approach
System approach to management
Continual improvement
Factual approach to decision making
Mutually beneficial supplier relationships

16. 10. Briefly explain the ISO 9001:2000 (Requirements) document for quality assurance.
The five major parts of this document are as follows.
Part 4. Systemic requirements
Part 5. Management requirements
Part 6. Resource requirements
Part 7. Realization requirements
Part 8. Remedial requirements