Why perform quality evaluation?
Many release and/or phase acceptance decisions are
made with a degree of uncertainty since only hazy
statements can be made about the results which are
available. An unambiguous statement about results is only
possible on the basis of a reasoned assessment of the
object in question. This raises the question of the
quality of the object.What should we understand
here as quality?
There is no such thing as good or bad quality in
itself. Quality can only be evaluated on the basis of
defined quality criteria. These result from the
requirements made on the object.
Where are quality criteria obtained from?
Quality criteria can be drawn from a whole range of
standpoints (from the user's perspective, from a
maintenance perspective, etc.). It is also possible to
define different degrees of quality fulfillment and/or
metrics which allow the relevant criterion to be
assessed. The quality (a term which in itself contains no
quantity such as high, low, etc.) consists then of the
degree to which it fulfils one or all of the criteria
defined for the object. The quality may then satisfy (or
not) the requirements as per the criteria.
What are quality criteria?
According to Siemens standard SN 77 350, the
following quality features apply for software
- Reliability
- Degree to which it fulfils its defined function
- User friendliness
- Time response
- Consumption behavior
- Maintenance-friendliness
- Portability
Within these features there are additional subfeatures
such as learnability and usability (subfeatures of
user-friendliness).
If these features are assigned values (e.g. point
values, time values, etc.), the result is objective
quality criteria.
How are evaluations performed?
Software can be evaluated against the prespecified
quality criteria by
- measurement
- point rating
- or other project-specific evaluation methods
This can take place, for example, after the
corrections following on from reviews and tests
("the result is ready"). The evaluation result
can constitute the reasoned basis for the release
decision.
Where do I find out how to make a detailed quality
evaluation?
The brochure 'Evaluation of Software Quality' (in
German) is available from PSE QM. PSE QM QI provides
advice on metrics.
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