A process to improve the accuracy of MkII FP to COSMIC size conversions: Insights into the COSMIC method design assumptions

Abstract

Converting software sizes measured by one Functional Size Measurement (FSM) method to another is usually achieved by measuring the size of a sample of software items by both methods and deriving a statistical correlation curve that can be used for converting the whole set of measurements. This paper describes a ‘calculation method’ to convert functional sizes measured by the MkII FSM method to COSMIC functional sizes. The method exploits some common features of both FSM methods and uses ‘functional profiling’ of measurements in order to form homogeneous datasets suitable for conversion. Applying the method to measurements of the same software by both FSM methods confirms that the calculated COSMIC sizes are more accurate than statistically-converted sizes. Comparing the way in which the two methods measure functional size and the results of the conversion study yields significant, positive insights into the design assumptions of the COSMIC FSM method.