Conversion from IFPUG FPA to COSMIC: Within-vs Without-Company Equations

Companies have employed for years 1st generation Functional Size Measurement (FSM) methods, e.g., IF PUG Function Points Analysis (FPA), collecting IF PUG-based historical data useful for benchmarking and estimation purposes. With the advent of 2nd generation FSM methods (e.g., COSMIC) the need for resizing past projects utilizing these new measures arises. The adoption of 2nd generation FSM methods has been limited both by the costs for acquiring new know-how and the need for resizing the historical data. Conversion equations represent a useful mean to facilitate the migration towards 2nd generation FSM methods. Previous works showed a significant correlation between the COSMIC and the FPA sizes. In our study we applied the conversion equations found in those works (i.e., Without-company equations) to resize 25 IF PUG-based projects coming from a single software company. We compared their use with respect to two conversion equations built by using two small subsets (i.e., 5 and 10 projects) from that company data (i.e., Within-company equations). We aimed to verify whether the use of within-company equations built using few projects could provide more accurate conversions than those achieved by applying without-company equations. Our analysis revealed that the within-company equations performed significantly better than the without-company ones. Thus, companies should develop their own equations rather than using without-company conversions.