Chapter 2 : Quality Framework and ISO-9126
Topics covered in this snack-sized chapter:
ISO-9126 provides a hierarchical framework for quality definition, organized into quality characteristics and sub-characteristics.
ISO- 9126 is called Software
Product Evaluation. It offers a comprehensive framework to describe many attributes and properties associate with quality.
There are six quality characteristics:
A set of functions and their specified properties.
The functions are those that satisfy stated needs.
The software performs as per the
requirements and specifications.
- Testing is used to verify that the requirements are met.
Obviously this is the most basic of quality factors but can be problematic for large, complex software.
Sub-characteristics include:
A set of attributes that bear on the capability of software to maintain its level of performance under stated conditions for a stated period of time.
It is also defined as the probability of failure-free operation.
Sub-characteristics include:
A set of attributes that bear on the effort needed for use, and on the individual assessment of such use, by a stated set of users.
It can be measured in terms of:
- Physical and intellectual skill required to learn the system.
- Time required becoming moderately efficient in the use of the system.
- The net increase in productivity over the system it replaces.
- A subjective assessment of user’s attitude towards the system.
Sub-characteristics include:
A set of attributes that bear on the relationship between the level of performance of the software and the amount of resources used, under stated conditions.
We can measure efficiency indirectly by
measuring the amount of time (execution efficiency) or storage (storage efficiency) needed when running the software through a particular compiler, under a specific OS, on a designated hardware architecture.
- Sub-characteristics include:
A set of attributes that bear on the effort needed to make specified modifications.
Maintainability cannot be measured directly.
- MTTC (mean time to change) is the time it takes to analyse, design, and implement the change.
- Maintainable programs have a lower MTTC.
The sub-characteristics include:
A set of attributes that bear on the ability of software to be transferred from one environment to another.
The sub-characteristics include:
Taking into consideration their specific business and market environment many companies associated with different application domains have adapted and customized existing quality frameworks to define quality for themselves.
CUPRIMDS is a concrete example of this. It stands for:
Capability: Capability is the ability to perform actions.
Usability: Ease of use accessibility.
Reliability: Robustness and stability of the software under difficult working condition.
Installation: Installation and configuration support.
Maintainability: Features to update the software and to receive defect fixes.
Documentation: Correctness, completeness and usability of the manuals.
Quality in use metrics measure the extent to which a product meets the needs of specified users to achieve specified goals with effectiveness, productivity and satisfaction in a specified context of use.
Quality in use is the user’s view of the quality of a system containing software, and is measured in terms of the result of using the software, rather than properties of the software itself.
The relationship of quality in use to the other software quality characteristics depends on the type of user:
- The end user for whom quality in use is mainly a result of functionality, reliability, usability and efficiency.
- The person maintaining the software for whom quality in use is a result of maintainability.