The document discusses software quality assurance. It defines quality as characteristics like correctness, maintainability, and usability. Quality assurance involves establishing procedures and standards for quality. Key concepts are quality planning, quality control, and cost of quality. Formal technical reviews are an effective way to improve quality by finding defects before release. The document also discusses software quality attributes, process-based quality, metrics like cohesion and coupling that impact modularity and reusability, and factors that influence understandability.

1. Software Engineering
WEEK 9
Software Quality Assurance
Sibel Kuzgun Akın

2. What is the quality?
● Quality refers to any measurable
characteristics such as correctness,
maintainability, portability, testability,
usability, reliability, efficiency, integrity,
reusability and interoperability.
● Quality, simpicically means that a product
should meet its specification.

3. Concepts of the quality
● Quality assurance
– Establish organisational procedures and standards for
quality
● Quality planning
– Select applicable procedures and standards for a
particular project and modify them if required
● Quality control
– Ensure those procedures and standards are followed by
the software development team
● Cost of quality
– Includes all costs incured in the pursuit of quality or in
performing quality related activities such as appraisal
costs, failure costs and external failure costs.

4. “It is better to try to keep a bad thing from happening
than it is to fix the bad thing once it has happened.”
● https://www.seguetech.com/rising-costs-defects/

5. Software Quality Assurance
● IEEE Glossary: Degree to which a system,
component or a process meets
– (1) specified requirements
– (2) customer or user needs or expectations
● ISO: The totatily of feautures or
characteristics of a product or service that
bear on its ability to satisfy specified or
implied needs.

6. Software Quality Attributes
● Safety
● Security
● Realiability
● Resilience
● Robustness
● Understandability
● Testability
● Adaptability
● Modularity
● Complexity
● Portability
● Usability
● Reusability
● Efficiency
● Learnability

7. Process based quality

8. Quality management and
software development

9. Formal technical reviews
● Purpose is to find defects before they are
passed on to another software engineering
activity or released to the customer.
● Software engineers and others conduct
formal technical reviews for software
engineers.
● Using formal technical reviews
(walkthroughs or inspections) is an effective
mean for improving software quality.

10. Software reviews
● To uncover errors in function, logic or
implementation for any representation of
the software.
● To verify that software meets its
requirements.
● To ensure that software representation
meets predefined standards.
● To achieve software development in a
uniform manner.
● To make projects more managable.

11. Product and process standards
Product standards
● Design review form
● Document naming
standards
● Procedure header
format
● Programming style
standard
● Project plan format
● Change request form
Process standards:
● Design review conduct
● Submission of
documents
● Version release process
● Project plan approval
process
● Change control process
● Test recording process

12. Internal and external attributes

13. Software Metrics
Software metric is a generic term that covers
● Cost and effort estimation models and
measures
● Productivity measures and models
● Quality models and measures
● Control and assurance
● Data collection
● Algorithmic / computational complexity
● Performance evaluation and models

14. Software Metric
● Software metric is a number derived from a
process, product or resource.
● Metrics can help address some of the most
critical issues in software development and
provide support for planning, monitoring,
controlling, and evaluating the software
process.
● We may use software metrics to collect
data from software to achieve quality
goals.

15. Cohesion
● Cohesion is an attribute of individual syb-
systems, describing their relative functional
strength, i.e. the extent to which the
individual sub-system components are
needed to perform the same task.
● We want to increase cohesion in order
to improve software modularity and
reusability.

16. Categories of cohesion
6. Functional cohesion Good
5. Sequential cohesion |
4. Communicational cohesion |
3. Procedural cohesion |
2. Temporal cohesion |
1. Logical cohesion |
0. Coincidental cohesion Bad

17. Functional cohesion
● If a function does a single, well defined
task it has functional cohesion.
● The functional strength is inversely
proportional to the generality of a function.
● The functional cohesion of a function can
be indirectly measured by measuring its
generality.
● Control variables increase the functionality
by twice that of data variables.

18. Sequential cohesion
● If the function performs more than one
task, but these tasks occur in an order
which was described in the specification,
there is sequential cohesion.

19. Communicational cohesion
● If the function performs more than one
task, but these tasks are all on the same
body of data, then its cohesion is
communicational.

20. Procedural cohesion
● There is procedural cohesion if the function
performs more than one task, and these
tasks are only related to a general
procedure effected by the software.

21. Temporal cohesion
● The function is temporally cohesive if it
performs more than one task, and these
tasks are only related logically.

22. Coincidental cohesion
● In the case of coincidental cohesion, the
function performs more than one task, and
these tasks are unrelated.

23. Another classification of cohesion
● Functional cohesion
● Data flow cohesion
● Action bundling cohesion
● Logical bundling cohesion

24. Data flow cohesion
● It describes the interdependencies among
the different statements of the function
depending on processing of data.

25. Coupling
● Coupling is a measure of degree of
interdependence between subsystems.
● Coupling of a sub-system is the
dependence of it on the other sub-systems
or global elements.
● We want to decrease coupling to
improve modularity and reusability.

26. Types of Coupling
5. Content coupling Bad
4. Common coupling |
3. Control coupling |
2. Stamp coupling |
1. Data coupling |
0. No coupling Good

27. Coupling
● In the case of content coupling, a function
branches into, changes data or alters a
statement in another function.
● Common coupling means that two
functions refer to the same global data.
● If a function passes a variable to another
function with the intention of controlling its
behavior, that is control coupling.

28. Coupling
● If two functions accept the same record
type as a parameter, there is a stamp
coupling between them.
● In the case of data coupling two functions
communicate by parameters which do not
contain any control element.
● No coupling means there is not any
communication between modules

29. Modular Dependency
Compile time dependency versus link time
dependency
Structured programming:
● Sharing extern variables among modules
● Including header files
● Calling functions of other modules
Object oriented programming:
● Using other classes
● Inheriting from other classes

30. Reusability
● Reusability is the degree to which a
component can be used in more than one
software system, or in building other
components, with little or no adaptation.
● We want to increase reusability.

31. Size
● LOC (lines of code)
● Number of
functions
● Number of classes
● Number of modules
● Module length
● Comment lines
● Blank lines
● Identifier length
Size of a system is a property that describes
its greatness.

32. Size Metric

33. Style
● Function length
● Identifier length
● Indentation
● Comments
● Blank lines
● Line length
● Embedded spaces
● Constants
● Number of reserved
words and standard
functions
● Included files

34. Understandability
● Understandability is defined as the amount
of programmer effort required to
understand a software component.
● We want to increase the understandability
of a program.
● Understandability affects the testability
maintainability of a program. If
understandability increases, maintainability
and testability increases.

35. Understandability: Language
● Different naming styles can significantly
affect the visual appearance of programs.
● Intuitively, the programs with natural
names are said to be more understandable
than the programs with abbreviated names.
● Smaller languages are usually easier to
understand than larger languages. So, as
the number of symbols in a language
increases, the understandability decreases.

36. Understandability: Unstructuredness
Unstructuredness in a program decreases
understandability.
● Goto: NEVER EVER USE!
● Branching out of a loop
● Branching to the test statement of a loop
● Infinite loop
● More than one return statements
● Exit () statements