ABSTRACT
Introduction This chapter describes function-based sizing for software size definition, concentrating on the International Function Point User Group (IFPUG) counting standards. Additionally SEER-FBS (function-based sizing), which approximates function points with simple inputs for early estimation, is discussed. Uncertainties and risk related to function-based sizing are also examined. The David Consulting Group, authors of the primary book on function point counting state:
The most important planning metrics are those having to do with scope and size of the project. One of the most frequently used sizing metrics is function points. Function points measure functionality. A key advantage of function points is that they can be counted before design and coding begin by reference to the requirements specifications, assuming that those are, as they should be, comprehensive with respect to what the software product is supposed to do.1
