Function point

The function point is a "unit of measurement" to express the amount of business functionality an information system (as a product) provides to a user. Function points are used to compute a functional size measurement (FSM) of software. The cost (in dollars or hours) of a single unit is calculated from past projects. There are several recognized standards and/or public specifications for sizing software based on Function Point.

1. ISO Standards FiSMA: ISO/IEC 29881:2010 Information technology – Systems and software engineering – FiSMA 1.1 functional size measurement method. IFPUG: ISO/IEC 20926:2009 Software and systems engineering – Software measurement – IFPUG functional size measurement method. Mark-II: ISO/IEC 20968:2002 Software engineering – Ml II Function Point Analysis – Counting Practices Manual Nesma: ISO/IEC 24570:2018 Software engineering – Nesma functional size measurement method version 2.3 – Definitions and counting guidelines for the application of Function Point Analysis COSMIC: ISO/IEC 19761:2011 Software engineering. A functional size measurement method. OMG: ISO/IEC 19515:2019 Information technology — Object Management Group Automated Function Points (AFP), 1.0 The first five standards are implementations of the over-arching standard for Functional Size Measurement ISO/IEC 14143. The OMG Automated Function Point (AFP) specification, led by the Consortium for IT Software Quality, provides a standard for automating the Function Point counting according to the guidelines of the International Function Point User Group (IFPUG) However, the current implementations of this standard have a limitation in being able to distinguish External Output (EO) from External Inquiries (EQ) out of the box, without some upfront configuration. Function points were defined in 1979 in Measuring Application Development Productivity by Allan Albrecht at IBM. The functional user requirements of the software are identified and each one is categorized into one of five types: outputs, inquiries, inputs, internal files, and external interfaces.