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Many times I have been asked about differences between IFPUG Function Points and NESMA Function Points. Many people mix up these concepts, are IFPUG Function Points and NESMA Function Points the same? Without going into details, in this post I try to explain the similarities and differences between IFPUG and NESMA through a simple example.
We can say that the IFPUG Function Points and NESMA Function Points are cousins because they have the same grandfather, which are Allan Albrecht Function Points.
The NESMA was founded in 1989 as the NEFPUG (Netherlands Function Point Users Group. Nowadays, NESMA). The NESMA manual focused on the application of function point analysis to software enhancement and maintenance . (Interactive Timeline of History of Function Points)
Despite this divorce between IFPUG Function Point and NESMA Function Point, the counting guidelines of the NESMA and the IFPUG continuously came closer and closer. With the publication of IFPUG CPM 4.2 (2004) the last major differences between IFPUG and NESMA disappeared. Both the NESMA and the IFPUG now use the same concepts and terms, and the same rules and guidelines within FPA. Even in the last version of IFPUG Function Point Counting Practices Manual (4.3.1, 2010), in Part 3 Chapter 4 “Enhancement Projects and Maintenance Activity”, refers to NESMA for address the relationship between the functional size of the enhancement and the effort required to implement that enhancement.
The Philosophy of each method is different. IFPUG Function Points measure the size of the ship that I will paint (either new or changed). In the other hand, NESMA Function Points focus on measure the size of what I’m going to paint (if the functionality is added, the IFPUG project function point count and NESMA is the same but if the functionality is changed, NESMA calculates the percentage of the ship that I will paint).
A work order is sent to a painter for painting an entire ship.
IFPUG: The Functional Size of this Development project is 10 FP.
APRENDE A MEDIR Y ESTIMAR PROYECTOS DE SOFTWARE
- ¿Por qué? Aprende a justificar porque se deben medir los proyectos de software
- ¿Para qué? Aprende para que sirve una medición y los beneficios que obtienes con ellas.
- ¿Cómo? Aprende métodos de estimación y medición como: COCOMO 81 y COCOMO 2000, Putnam, Estimación de 3 puntos, Puntos Función IFPUG, NESMA, MKII, COSMIC, SiFP, Puntos de Casos de Uso, SNAP, T-Shirt y un largo etc.
NESMA: The function point size of this work is 10 FP.
In both cases we could pay to the painter for each Function Point painted. We get information from a benchmark and we use a rate 1 € / FP. We will pay 10 € to the painter.
The IFPUG Functional Size and NESMA Functional Size is the same for added functions , both now use the same rules and guidelines within FPA.
(The impact factor for added functions is 1.00.)
A work order is sent to a painter to develop an adaptive maintenance for painting the ship. (enhancement project).
IFPUG: The Functional Size of this Enhancement project are 10 FP. (does not say anything about Percentage changed). The Functional size in Case 2 is the same than Case 1, IFPUG focus on functional size, not in what have been changed.
With IFPUG Function Point you cannot use the same rate than Case 1 (added functions). We need to use another rate for enhancement activities. We get information from a benchmark and we use a rate (for enhancement activities) 0,25 €/FP. We will pay 2,5 € to the painter.
NESMA: The painter will paint only a percentage of the ship, not all the ship (we suppose that the value of the impact factor is 25%). The ship size is 10 FP, but the painter not needs to paint all the ship, the enhancement function point size is 2.5 FP (The NESMA Functional size is the size that the painter has to paint, not the size of the ship).
With NESMA Function Point you can use the same rate than Case 1 (added functions). We could pay to the painter for each Function Point painted. We will pay 2,5 € to the painter (rate 1 € / FP).
(The impact factor for a transaction is determined from the percentage changes in the numbers of DETs and FTRs)
With IFPUG we need (at least) two different rates, one for development project and other for enhancement project.
With NESMA we can use the same rate for all projects.
NESMA tries to address the relationship between the functional size of the enhancement and the effort required to implement that enhancement .
You can use the method you want, but you need to know the differences between IFPUG Function Point and NESMA Function Point.