The document discusses different approaches to measuring software quality, including: 1. ISO 9126 which defines 6 quality factors: functionality, reliability, usability, efficiency, maintainability, and portability. 2. McCall's quality factors from 1977 which defines 11 factors and provides examples for each. 3. IEEE 982 which defines 9 classes of reliability measures including product measures like errors/faults/failures and process measures like management control. The document emphasizes that quality factors should be defined in requirements and measuring them indicates where improvement is needed.

1. Quality Factors

2. Question
 To know that quality has improved, it
would be helpful to be able to measure
quality.
 How can we measure quality?

3. ISO 9126 Software Quality Factors
1. Functionality
2. Reliability
3. Usability
4. Efficiency
5. Maintainability
6. Portability

4. McCall's Quality Factors (1977)

5. Define and give example of each
 Usability
 Integrity
 Efficiency
 Correctness
 Reliability
 Maintainability
 Testability
 Flexibility
 Reusability
 Portability
 Interoperability

6. Operability
Training
Communicativeness Usability
Input/Output volume
Input/Output gate Integrity
Access Control
Access Audit Efficiency
Storage efficiency
Execution Efficiency Correctness
Traceability
Completeness Reliability
Accuracy
Error Tolerance Maintainability
Consistency
Simplicity
Testability
Conciseness
Instrumentation
Expandability
Flexibility
Generality
Self-Descriptiveness Reusability
Modularity
Machine Independence Portability
Software System Independence
Communications Commonality Interoperability
Data Commonality

7. Reality Check…
Q: So, how does that long list help us
with SQA?
A: Most, if not all, of those factors
should be covered explicitly in the
software requirements document.
A: Measuring those factors tell us
where we need improvement.

8. IEEE 982
" Reliability is an estimation of system failure-freeness. … A
constructive approach to reliable software seeks to remove the root
causes of this class of system failure through software development and
support processes that promote fault avoidance, early fault detection,
appropriately prompt removal, and system-designed fault tolerance.
The analysis of the errors, faults, and failures from previous
development and support processes can lead to improved future
processes. While the exact functional relationships are not proven, it is
through experience that the majority of failures are related to their
origins. Examples include the following:
 Incompletely defined user needs and requirements
 Omissions in the design and coding process
 Improper usage of the system
 Excessive change activity

9. IEEE 982
Nine Classes of Measures
 Product Measures
1. errors, faults, failures
2. mean-time-to-failure
3. realibility growth and projection
4. remaining products faults
5. completeness and consistency
6. complexity
 Process Measures
1. management control
2. coverage
3. risk, benefit, cost evaluation

10. More Info on Quality Metrics
 Links to
 IEEE 982
 particularly interesting
 section 4
 appendices
 National Institute for Standards and Technology
 NASA Quality Factors