On the Seven Misconceptions about Functional Size Measurement

Among the various approaches to software size measurement, Functional Size Measurement has been widely recognized for its usability in early phases of software development cycles and its independence from implementation language, development method and technology. Starting from its introduction with the original Function Point Analysis method in 1979, functional size has been a favored input to estimation and productivity models. As a result of the search for solutions to emerging measurement needs and the advancements in the discipline of software measurement, FSM concepts have been redefined and measurement methods have matured with notable contributions from the ISO standardization process. Despite the progress towards an unambiguously defined and versatile measure in software engineering, several misconceptions about FSM in software community keep on leading to misuse of functional size and unproductive measurement practices. While such misperceptions results in disappointment and wasted resources, an important consequence is the disinterest in FSM. In this paper, we elaborate seven misconceptions in FSM. We review functional size and FSM by discussing the misconceptions. Our purpose is to give a state-of-the-art presentation of functional size and to guide software practitioners and researchers in applying FSM principles properly in their practices and software engineering methods and models.