Function points are a measure of the size of computer applications and the projects that build them. The size is measured from a functional, or user, point of view. It is independent of the computer language, development methodology, technology or capability of the project team used to develop the application.
In the late seventies, IBM felt the need to develop a language independent approach to estimating software development effort. It tasked one of its employees, Allan Albrecht, with developing this approach. The result was the function point technique.
In the early eighties, the function point technique was refined and a counting manual was produced by IBM's GUIDE organization. The International Function Point Users Group (IFPUG) was founded in the late eighties. This organization produced its own Counting Practices Manual. In 1994, IFPUG produced Release 4.0 of its Counting Practices Manual. While the GUIDE publication and each release of the IFPUG publications contained refinements to the technique originally presented by Albrecht, they always claimed to be consistent with his original thinking. In truth, it is still very close considering the nearly two decades that have elapsed since Albrecht's original publication!
During the eighties and nineties, several people have suggested function point counting techniques intended to substantially extend or completely replace the work done by Albrecht. Some of these will be briefly discussed in this FAQ. However, unless otherwise specified, information in this FAQ is intended to be consistent with IFPUG Release 4.0.
The fact that Albrecht originally used it to predict effort is simply a consequence of the fact that size is usually the primary driver of development effort. The function points measured size.
It is important to stress what function points do NOT measure. Function points are not a perfect measure of effort to develop an application or of its business value, although the size in function points is typically an important factor in measuring each. This is often illustrated with an analogy to the building trades. A three thousand square foot house is usually less expensive to build one that is six thousand square feet. However, many attributes like marble bathrooms and tile floors might actually make the smaller house more expensive. Other factors, like location and number of bedrooms, might also make the smaller house more valuable as a residence.
Read more about Function Points here:
http://ourworld.compuserve.com/homepages/softcomp/fpfaq.htm
In the late seventies, IBM felt the need to develop a language independent approach to estimating software development effort. It tasked one of its employees, Allan Albrecht, with developing this approach. The result was the function point technique.
In the early eighties, the function point technique was refined and a counting manual was produced by IBM's GUIDE organization. The International Function Point Users Group (IFPUG) was founded in the late eighties. This organization produced its own Counting Practices Manual. In 1994, IFPUG produced Release 4.0 of its Counting Practices Manual. While the GUIDE publication and each release of the IFPUG publications contained refinements to the technique originally presented by Albrecht, they always claimed to be consistent with his original thinking. In truth, it is still very close considering the nearly two decades that have elapsed since Albrecht's original publication!
During the eighties and nineties, several people have suggested function point counting techniques intended to substantially extend or completely replace the work done by Albrecht. Some of these will be briefly discussed in this FAQ. However, unless otherwise specified, information in this FAQ is intended to be consistent with IFPUG Release 4.0.
The fact that Albrecht originally used it to predict effort is simply a consequence of the fact that size is usually the primary driver of development effort. The function points measured size.
It is important to stress what function points do NOT measure. Function points are not a perfect measure of effort to develop an application or of its business value, although the size in function points is typically an important factor in measuring each. This is often illustrated with an analogy to the building trades. A three thousand square foot house is usually less expensive to build one that is six thousand square feet. However, many attributes like marble bathrooms and tile floors might actually make the smaller house more expensive. Other factors, like location and number of bedrooms, might also make the smaller house more valuable as a residence.
Read more about Function Points here:
http://ourworld.compuserve.com/homepages/softcomp/fpfaq.htm
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