Functional Size Measurement Methods (FSMMs)

There are currently five different ISO/IEC Functional Size Measurement Method standards, four of which are outlined in this chapter, plus the IFPUG method (unadjusted), which was described in an earlier chapter. Additionally, there are variants of the IFPUG method and also of other methods that purport to measure the size of software. For convenience of the reader, the ISO/IEC standards are included here, and the other sizing measures are included in the chapter “Variants of the IFPUG Function Point Counting Method.”

Functional Size Measurement is a term coined by the International Organization for Standardization/International Electrotechnical Commission (ISO/ IEC) in its suite of standards numbered 14143-1 through 14143-6. The definition and framework standard of the series is ISO/IEC 14143-1 Software and Systems Engineering – Software Measurement – Functional Size Measurement – Definition of concepts. This standard was most recently updated and published in 2007, replacing the first published version in 1998. Note that ISO/IEC standards have a lifespan of 5 years from the date of publication, after which they must be reviewed by ISO/IEC to ensure ongoing relevance. ISO/ IEC working groups can then reaffirm a standard as it is, withdraw it, or update it (and a new work item proposal is launched to revise it). The 14143-1: 2007 standard reaffirmed the standard and then republished it via an ISO-specific process called a technical corrigendum to correct minor technical defects and editorial defects.