Page 269 - DCAP304_DCAP515_SOFTWARE_PROJECT_MANAGEMENT

Unit 13: Software Quality

Notes

Notes ISO 9126 Observations
For the most part, the overall structure of ISO9126-1 is similar to past models, McCall
(1977) and Boehm (1978), although there are a couple of notable differences. Compliance
comes under the functionality characteristic, this can be attributed to government
initiatives like SOX. In many requirements specifications all characteristics, that are
specified, that are not pure functional requirements are specified as Non-
Functional requirements. It is interesting to note, with ISO9126, that compliance is seen
as a functional characteristic.
Using the ISO 9126 (or any other quality model) for derivation of system requirements
brings clarity of definition of purpose and operating capability.

For example, a rules engine approach to compliance would enable greater adaptability,
should the compliance rules change. The functionality for compliance could be implemented
in other ways but these other implementation methods may not produce as strong an
adaptability characteristic as a rules, or some other component based, architecture.
Also, a designer typically will need to make trade offs between two or more characteristics
when designing the system. Consider highly modularized code, this code is usually easy
to maintain, i.e. has a good changeability characteristic, but may not perform as well (for
CPU resource, as unstructured program code). On a similar vein a normalized database
may not perform as well as a not normalized database. These trade offs need to be identified,
so that informed design decisions can be made.
Although ISO 9126-1 is the latest proposal for a useful Quality Model, of software
characteristics, it is unlikely to be the last. One thing is certain, the requirements (including
compliance) and operating environment of software will be continually changing and
with this change will come the continuing search to find useful characteristics that facilitate
measurement and control of the software production process.

Self Assessment

Fill in the blanks:

1. SQA is not the only ……………….. activity in a project.
2. A procedure defines how an activity will be conducted. ……………….. are defined in
plans, such as a Software Configuration Management Plan.

3. Software products are ……....………… , user manuals and technical documents, such as an
Architectural Design Document.

4. The ………………...... of software quality that assures that the standards, processes, and
procedures are appropriate for the project and are correctly implemented.

13.3 Measuring Software

Measuring software is a powerful way to track progress towards project goals.

As Grady states, “Without such measures for managing software, it is difficult for any organization
to understand whether it is successful, and it is difficult to resist frequent changes of strategy.”
Appropriately selected metrics can help both management and engineers maintain their focus
on their goals.

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