The form should be as generic as possible so as to collect the type of data needed for a variety of models, not just a specific model. Of course, if the model is known, then a specific input form makes sense. An example of a generic form is the data form included in the Space and Missiles Center Software Database User's Manual . A potential drawback to such generic forms is that they tend to be lengthy and cumbersome to complete and use. One limitation of these results is that the models were not calibrated.
Calibration can and does improve model accuracy.
Software maintenance cost accuracy is in an even worse state. An Air Force study performed by Ferens in 1983 and published in the ISPA Journal of Parametrics, concluded that no software support cost models could be shown to be accurate. Unfortunately, the results of that study have never been refuted. Maintenance cost estimating is further complicated in that traditional estimating practices do not always apply. In the block change process used by the Air Force in supporting weapons software, however, the time and number of personnel are fixed, and the amount of work that can be done within those constraints must be estimated.