Function Point Analysis

Function point analysis (FPA) can be used to measure the size of a proposed software system (in function points), from its specifications. Unadjusted function points, which are based on the information processed by the software system, are calculated first. The unadjusted function point total is then modified by an adjustment factor (application characteristics adjustment factor or technical complexity factor (TCF), which takes into account the various technical and other factors involved in developing and implementing the information processing requirements (ease of use, ease of maintenance, etc.), that can influence the final size of a software application. Function points are thus a composite metric introduced with the aim of measuring the function value that a software system provides to the user. As a unit of measure function points are claimed to be more readily understandable by business users. The function point measure is a dimensionless number independent of the language in which the software is implemented and, because of its independence from development language and technology, FPA can be used to compare the productivity and quality of competing languages and technologies. Since FPA's introduction in 1979, FPA has undergone several changes in its counting procedures. The modifications are attempts to cater for changes that have occurred in software development methodologies and are discussed here. FPA can be useful for planning purposes because function point counts may be obtained from software requirements specifications that are based on the owner–user requirements model. Thus they are available early in the development cycle, are usually easier to determine than lines of code from a requirements specification, and in some cases provide an earlier, more accurate prediction of software size than a LOC estimate. This article continues with a discussion of an outline of functionp oint computation, and follow with the uses, advantages, and disadvantages of function points, and their extensions to FPA. Our discussion then continues with a glance at the International Standard for Functional Size Measures, a function point analysis summary, and a short discussion on software productivity measurement. Keywords: function point computation; uses; advantages; disadvantages; extensions; modifications; productivity; pitfalls; measurement