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Evaluation process

Source ISO 9126: 1991, 5.3.

The evaluation process consists of three stages and it may be applied in every appropriate phase of the life cycle for each component of the software product:

Quality Requirement Definition: The purpose of the initial stage is to specify requirements in terms of quality characteristics and possible subcharacteristics. Requirements express the demand of the environment for the software product under consideration, and must be defined prior to the development. As a software product is decomposed into major components, the requirements derived from the overall product may differ for the different components.

Evaluation Preparation: The purpose of the second stage is to prepare the basis for evaluation. This stage consists of three components:

Quality metrics selection
: The manner in which quality characteristics have been defined does not allow their direct measurement. The need exists to establish metrics that correlate to the characteristics of the software product. Every quantifiable feature of software and every quantifiable interaction of software with its environment that correlates with a characteristic can be established as a metric. [...] Metrics can differ depending on the environment and the phases of the development process in which they are used. Metrics used in the development process should be correlated to the user respective metrics, because the metrics from the user's view are crucial.
Rating levels definition
: Quantifiable features can be measured quantitatively using quality metrics. The result, the measured value, must be interpreted as a rated value, i.e. divided into ranges corresponding to the different degrees of satisfaction of the requirements. Since quality refers to given needs, no general levels for rating are possible. They must be defined for each specific evaluation.
Assessment criteria definition
: To assess the quality of the product, the results of the evaluation of the different characteristics must be summarized. The evaluator has to prepare a procedure for this, using, for instance, decision tables or weighted averages. The procedure usually will include other aspects such as time and cost that contribute to the assessment of quality of a software product in a particular environment.
Evaluation Procedure:

The last step of the Evaluation Process Model is refined into three steps, namely measurement, rating and assessment.

For measurement, the selected metrics are applied to the software product. The result is values on the scales of the metrics.
In the rating step, the rating level is determined for a measured value.
Assessment is the final step of the software evaluation process where a set of rated levels are summarized. The result is a statement of the quality of the software product. Then the summarized quality is compared with the other aspects such as time and cost. Finally managerial decision will be made based on the managerial criteria. The result is a managerial decision on the acceptance or rejection, or on the release or no-release of the software product.

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Next: Maintenance of software products Up: Guidelines Previous: Evaluation of importance