Convertibility of Function Points to COSMIC-FFP: Identification and Analysis of Functional Outliers

COSMIC-FFP (ISO 19761) represents the second generation of functional size of the software, based on its ease of understanding and use and it is applicable to various kinds of software applications; this new method has achieved rapidly an ISO recognition as an international standard as well as market acceptance in various countries. Several organizations are therefore interested in using convertibility ratios between COSMICFFP and first generation of functional size measurement (in particular Function Point Analysis – FPA ISO 20926), in order to leverage data from their historical databases of software measures. Previous convertibility studies have indicated that convertibility of FPA to COSMIC-FFP can be simple, with a very good correlation for most MIS projects, but that there are some outliers for which convertibility is less straightforward. This study analyzes a new data set of 14 projects measured with both sizing methods, and for which measurement results are available at the detailed level. The analysis reported here identifies reasons why, for some MIS projects, convertibility is not so straightforward. This analysis also provides lead indicators to identify outliers for convertibility purposes.