Economical Measurements (The Limits of Automation)

The functional size of an application should be measured regularly in order to determine the growth and hence the development productivity of each release or increment. Only by comparing cyclic measurements, improving or worsening effects can be identified. Furthermore the organisation gets empirical productivity values which are the key for cost estimations of new development projects (see: Measuring Productivity in Software Development). 

Experience shows that cyclic measurements will be neglected if the accociated effort is too high. Measuring techniques based on counting rules allow a high degree of automation by mapping the objects to be counted to design features of an existing application and implementing the according scripts or programs for counting. The investment in implementing these script or programs quickly pays for itself when repeated measurements do not require anymore manual effort. Possible targets for automated counting are:

• Dialog models represented by XML or XHTML files as being used by many GUI frameworks

• XML schemas defining interface or message structures

• Meta data of a DBMS including information about tables and attributes

When applying automated measurement processes which have a stronger focus on design features than on the use cases of a system there is a risk of inaccurateness if counting objects have been used multiple times by the application design. An example of this is the comparison of two applications A and B, which are different implementations of the same use cases:

• At application A similiar dialogs have been implemented separately and partially redundant.

• At application B a generic dialog has been implemented which automatically adapts according to the use case respectively invocation. 

An automated size measurement based on design features will result in a lower value for application B, which is wrong because both applications are implementations of the same use cases. In the worst case this will promote bad development practice (copy & paste) and poor design, if developers try to increase the measured productivity by creating redundant counting objects. Actually this is fatal in several ways, because the reuse of components and services is one of the most important keys to sustainably increase productivity and improve maintainability.

Conclusion: Automated measuring techniques based on design features are necessary to make size measurements practicable at all. However a side effect is the limited comparability of applications with different degrees of reutilization.