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Object-oriented software metrics

For the measurement of software products so-called software metrics are used, which quantify different characteristics of software products and processes. The classical software metrics presented in the 70's and 80's after Halstead, McCabe or computation mountain as well as the LOC metric are assigned to the group of the conventional software metrics. To it the extent metrics belong, which determine the "size" of a software under different aspects. That can be both the number of coded lines as with Lines OF code (LOC), the linkage of the number of operators and operands (Halstead) and the process-oriented beginning of the Function POINT metric.

A different way points the McCabe metric, which includes the logical structure among other things the nesting depth of loops into the measurement. According to the Rechenberg metric, the aspect of measuring software complexity is emphasized, which is also commonly referred to as the data structure metric. The number of variables, their validity and lifetime as well as their referencing are integrated into the measurement. Another conventional method is the so-called style metric, which is limited to determining the proportion of comments in the source code.

A result of researches of more recent date are the so-called object-oriented software metrics. These consider with the measurement of software the summary of data structures and the methods applicable on it to an object, its relations to other objects as well as the general structure characteristics of object-oriented programming - as there for example data encapsulation, inheritance, classes, methods and abstraction are. For the better classification of these metrics the following levels can be differentiated:

Method level measurement Here the characteristics of methods are measured. Conventional methods such as Lines-of-Code (LOC) or McCabe can still be used for this purpose.

Measurement on class level Here the structure characteristics of classes are measured. As measure for it the following metrics are suitable: Response for a Class( RFC), Weighted Methods for Class(WMC) and Lack of Cohesion in Methods( LCOM).

Measurement of inheritance hierarchies Here, the structures created by inheritance and abstraction are considered. The Number of Children ( NOC) method is a suitable measure for this.

Measurement of aggregation hierarchies Here a measure for the linkage of classes among themselves is determined. The Coupling between Objects( CBO) method is suitable for this.

In general, the metrics mentioned are criticized for their partial lack of theoretical foundation and the exclusive measurement of trivial facts.

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Englisch: Object-oriented software metrics
Updated at: 30.11.2009
#Words: 398
Links: measurement, software (SW), Halstead, McCabe, loss of cell (LOC)
Translations: DE
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