Function point sizing: Structure, validity and applicability

This paper reports on a study carried out within a software development organization to evaluate the use of function points as a measure of early lifecycle software size. There were three major aims to the research: firstly to determine the extent to which the component elements of function points were independent of each other and thus appropriate for an additive model of size; secondly to investigate the relationship between effort and (1) the function point components, (2) unadjusted function points, and (3) adjusted function points, to determine whether the complexity weightings and technology adjustments were adding to the effort explanation power of the metric; and thirdly to investigate the suitability of function points for sizing in client server developments. The results show that the component parts are not independent of each other which supports an earlier study in this area. In addition the complexity weights and technology factors do not improve the effort/size model, suggesting that a simplified sizing metric may be appropriate. With respect to the third aim it was found that the function point metric revealed a much lower productivity in the client server environment. This likely is a reflection of cost of the introduction of newer technologies but is in need of further research.