Version: 2.2.1
Publication date: 2009
23 pages
ISBN: 978-90-76258-13-3


Thanks to presentations world wide and discussion groups on the internet, the Nesma experimental method FPA for Software Enhancement has literally become world famous. Nesma offers this Guide at no charge to the international software metrics community for further research.


Function point analysis is established internationally as a method for determining the scope and functional size of software from an assessment of the user requirements. The IFPUG “Function Point Counting Practices Manual” and the Nesma FPA counting practices manual “Definitions and Counting Guidelines for the Application of Function Point Analysis” both follow the “Albrecht” method and describe how to apply the method to implemented systems, software development and software enhancement. Application of the method to software enhancement is not well developed; other priorities have prevented a more considered treatment of this aspect of its application in the past.
Function point analysis has been applied extensively to the development of new software. Its use in this respect is well established and is supported by a wealth of research and practical experience. It is now appropriate to explore in greater depth the application of FPA to software enhancement and maintenance. Users of software metrics need to know whether FPA can be successfully applied to software enhancement and, if so, in what way and within what constraints. Consideration of these issues led NESMA to form the working group on “FPA for Enhancement and Maintenance”.
These guidelines apply FPA for enhancement projects, adjusting the regular weight of a function impacted by the enhancement project by an impact factor. The impact factor depends on the degree in which the function is enhanced by the project.
The guidelines are universally applicable, so also using the IFPUG CPM 4.3 FPA guidelines as your basic FPA measure.


The Guide is intended for anyone with an interest in the management of enhancements to an information system.
The Guide describes an objective and replicable method for assessing the scope and size of an enhancement project. The method is objective in that the results obtained are independent of the person applying the method; the result obtained is bona fide in that two different people using the same guidelines obtain the same result. The method is replicable in that a particular outcome can be determined a priori, and the same outcome can be produced on the second and subsequent applications of the method.

Intended Audience

The Guide is intended for anyone who performs function point analysis and wants to measure the size of enhancement projects more precisely. It is assumed that the reader is familiar with the standard FPA method.

Scope of the Research

NESMA considered the application of FPA to software enhancement from the perspective of the standard function point analysis method. The result of this work, embodied in these guidelines, is a method applicable to software enhancement and testing that is strongly related to the standard FPA method. The term Enhancement Function Point Analysis (EFPA) is used to differentiate the method from the standard function point analysis method.


The method has been tried in practice. However, NESMA does not claim that the method in its current form has been validated scientifically. Additional research and practical use is necessary to demonstrate the validity of the method.
By offering this guide to the international functional software measurement community, NESMA wants to advance the application of function point analysis to enhancement projects and to broaden the understanding of measurement applied to software enhancement. NESMA is not responsible for any use of this method or for the results obtained from its application.
Comments and suggestions for further improvement of this method may be sent to

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