Formalization Studies in Functional Size Measurement

Formalization Studies in Functional Size Measurement

Baris Özkan (Middle East Technical University, Turkey) and Onur Demirörs (Middle East Technical University, Turkey)
DOI: 10.4018/978-1-61350-456-7.ch710
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Functional size has been favored as a software size attribute that can be measured early in the software development cycles. Its characteristics of being independent of implementation language, technique and technology promoted the use in software cost estimation and other project management practices. It has been about three decades since Albrecht introduced the concept of functional size and a variety of measurement methods have been developed, some of which have been published by International Organization for Standardization (ISO). Although the concept is recognized in the software community, and there is a growing interest in Functional Size Measurement (FSM), the applications in software organizations have not been common as expected. The problems with FSM method structures and practices have been discussed to be the major factors to explain this situation. This chapter reviews the research papers that propose solutions to the problems with FSM via formalizations in FSM practices or related concept definitions. The associations of the formalization ideas to the abstract software models that represent the view of functionality for FSM methods are of particular interest of the chapter.
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Background On Functıonal Sıze And Functıonal Sıze Measurement

Software size has been associated with several attributes of software artifacts, documents and deliverables and software development practitioners have measured size using a wide range of metrics and methods. Fenton and Pfleeger (1996), defines software size as a multi attribute and describes it in terms of length, functionality and complexity. Among the various approaches developed to software size measurement, the measures and methods on quantifying the ‘functionality’ attribute have been widely accepted in practice. Software functional size measures the amount of functionality provided to the users. Functional Size Measurement (FSM) methods are mostly utilized in effort and cost estimation for software development and maintenance projects. Estimation errors are reported to be essential causes of poor management (Glass, 2002; Hughes, 2000) and the need for well established estimation models is so imperative that the relation between FSM and software cost, effort and time estimation can easily cause the misinterpretation of FSM methods as estimation models. Although Albrecht (1979) proposed the original idea as an approach to software estimation, the common approach in FSM methods and software community today is to separate FSM and software estimation as related but different concepts. Detailed explanation of size based cost estimation models and techniques can be found in (Matson, 1994; Abran, 2003; Boehm, 2003).

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