Function Point analysis using NESMA method

Function Point Analysis using NESMA

NESMA is Netherlands Software Metrics Association group which was set up in 1989. NESMA’s Function point methodology is a derivative of Alan Albrecht’s (IFPUG FP) method. NESMA claims that its method is meant for everyone who performs function point counts. For those using IFPUG (International Function Point Users Group) rules, NESMA standard can be valuable supplement. It consists of additional guidelines, hints, and examples that can be of value to the FPA counter.

NESMA released its first version of FP manual in Dutch in 1990. English version was released in 1997. Currently NESMA FPA manual version 2.1 is in use. This version provides rules and guidelines to calculate unadjusted Function Point count and is recognized by ISO (International Organization for Standardization).

In this document, I will try to brief 3 NESMA methods of counting Function Points. These three methods are – Indicative function point count, Estimated function point count and Detailed function point count. The methods, Estimated and Indicative function point counts have been developed by NESMA to enable function point counting early in the system life cycle. The NESMA indicative function point count is well known in the world and is referred to as "the Dutch method".

1.    Indicative FP count – It indicates the size of an application or a project based on either conceptual data model or normalized data model

If the data model in conceptual form is available then formula for # of FP is

# of FP = # of ILFs*35 + # of EIFs*15

If the data model is third normal form then following formula is used

# of FP = # of ILFs*25 + # of EIFs*10

Indicative FP count can almost be carried out at the end of requirements phase. It is good for a ballpark estimate. However this count will give a deviation of up to 50%

2.    Estimated FP count – It determines the number of functions for each function type and uses a standard value for complexity: Average for transactional functions and Low for data functions

 

The formula for deriving estimated FP count is as below.

 

# of ILFs*7 + # of EIFs*5 + # of EI*4 + # of EOs*5 + # of EQs*4

 

This method can be used whenever

a.    A quick estimate is required

b.    Detailed information about data/ transactions is unavailable

c.    Quick turnaround time is expected

d.    Accuracy of the count is not a concern

 

3.    Detailed FP count

The detailed FP count is the most accurate count in which all specifications needed for FPA are known in detail. This means transactional function types have been specified up to the level of data element types and referenced logical files and data function types have been specified up to the level of record types and data element types. This detailed function point count is similar to the unadjusted function point count of IFPUG method. This count costs more time and needs more detailed specifications as compared to Indicative and Estimated FP counts.