Functional and non-functional size measurement with IFPUG FPA and SNAP — case study

Abstract

Software size measures are probably the most frequently used metrics in software development projects. One of the most popular size measurement methods is the IFPUG Function Point Analysis (FPA), which was introduced by Allan Albrecht in the late-1970’s. Although the method proved useful in the context of cost estimation, it focuses only on measuring functional aspects of software systems. To address this deficiency, a complementary method was recently proposed by IFPUG, which is called Software Non-functional Assessment Process (SNAP). Unfortunately, the method is still new and we lack in-depth understanding of when and how it should be applied. The goal of the case study being described in the paper was to investigate how FPA and SNAP measurement methods relate to each other, and provide some early insights into the application of SNAP to measure the non-functional size of applications. The results of the study show that SNAP could help mitigating some well-known deficiencies of the FPA method. However, we have also identified some potential problems related to applying SNAP in a price-persize- unit pricing model.