To reach the quality assurance objects it is necessary to identify where we are and what we should do to reach these objects. To get such information, objective assessment using some quality models on collected data from the quality assurance activities is essential.
There are direct and indirect quality measures.
The direct quality measures need to be determined as piece of the activities to set quality objects, if such objects are quantified.
In many cases direct quality measures cannot be obtained until it is too late. For instance, for safety critical systems, post-accident measurements provide a direct measure of safety.
But because of the colossal harm related to these accidents, we are trying to do all possible to keep off such situations.
In order to control and monitor safety assurance activities different indirect measurements can be used.
There is also an growing price of correcting software bugs late instead of fixing them on early stages in common, because a hidden trouble may lead to other related defects, and the longer it stays not identified, the further removed it is from its root causes, thus making the identification of it even more complicate. Consequently, there is a powerful motive for early indicators of quality that measure quality indirectly.
Indirect quality measures may be used in different quality models to assess and forecast quality, through their established relations to direct quality measures based on historical data or data from other sources.
Consequently, it is necessary to select proper measurements, both direct and indirect, and models to provide quality assessment and feedback.