Function Point Estimation Technique

Project estimation is a quantitative assessment of the total amount of different variables including resources, duration and costs. The types of estimating techniques can be classified as –

Analogous or high level technique

Parametric or calculative technique

Bottom-up or detailed technique that includes all the ground level functions.

There are multiple project estimation techniques that are used by different organizations to analyse various projects. Some of the common techniques are:

Pure expert judgement

Historical data

Wideband Delphi

Source line of code

Use case point

Monte Carlo

Function point

Test case points

Function test points

Out of the above-listed techniques, function point analysis (FPA) is one of the most used in various project estimations.

What is the concept of function point?

The function count measures the functionality from user’s side and depends totally upon incoming and outgoing sources from user’s end. The basis of comparison is accounted by its available quantitative measure and organizational data. FPA has its principle decomposed into functional units. It essentially measures functionality that a user requests or receives and the 5 functional units incorporated into it are-

EI – It’s information entering the system

EO – It’s data which passes the boundary

EI – These are requests for having prompt access to info

ILF – It’s information residing within the system’s boundary

ELF – It’s the data stored in another system which is used only for reference purposes.

Function Point Analysis or FPA covers one very critical and difficult area of project planning that is size estimation. Users often face difficulty in establishing measuring units according to size of the system. Two of the most common methods by which one can do the evaluation are -

Function count

Lines of code

These 5 components can once again be sub-divided into two broadly divisible categories -

1.      Transactional function types

External Inquiry (EQ)

External Output (EO)

External Input (EI)

2.      Data functional types

EIF or External Interface Files

ILF or Internal Logical Files

A sneak peek into the history of function point:

Function Point was developed by Alan Albrecht in 1970s specifically for size estimation while working for IBM. It gained huge recognition as an ideal solution to the problem of size measurement. Function point is also regarded as the best system for measuring size of computer software.

Few of its special features are as follows:

Function point is free of any language tool or methodology used for implementation.

It can be estimated from requirements specification or design specification; hence, the estimation of the development effort in the initial stages.

Function point can directly connect with the necessary statements that can again easily be followed by re-estimate.

It is dependent on the external view of the system by the consumer. Even a non-technical user of the system software can have a better understanding of the function point estimation for measuring.