Function Point Analysis

Function Point Analysis

The objective of Function Point Analysis is to measure the size of software

-What is produced

-Not how it is produced

Because Function Point Analysis measures the requirements then it can be used to measure legacy mainframe systems, multi-layered client server systems, web-based systems or space station operating systems with equal facility.

Size can then be used to compare groups of projects, even when the projects are dissimilar

The International Standard - ISO 14143 defines what components a measurement method should contain. The International Function Point User's Group ( IFPUG) Counting practices Manual (CPM) is certified as conforming to this standard. The current version of the CPM is 4.3.1.

Within the IFPUG technique there are five function types:

• Data Stored within the System
• Data referenced on other systems

• Inputs
• Enquiries
• Outputs

To Measure each of the Function Types there is a 3 * 3 matrix giving the size and complexity. This matrix is different for each function type. Here is the input matrix as an example.

The types of functions that would be counted as inputs are:

• Add Property
• Amend Property

Terminology:

• an FTR is a logical file. A logical file is a group of dependent entites for example:
  • Property
  • Property Description
  • Property Rental Rates
  • Property Rental Rebates
  • Property Additional Charges
• a DET is non-repeating attribute or field for example:
  • PropertyId
  • Rental Amount
  • Rental Periodicity

Scoring:

Low scores 3 Function Points

Medium scores 4 Function Points

High scores 6 Function Points

 

Size is also afffected by the technical complexity of the software. For example if software is to be supported remotely then the support team will need access to the application and support tools. The IFPUG technique uses 14 characteristics to assess the technical complexity of the application. These include performance targets, supporting multiple sites, arithmetic complexityand componentisation of the code.

Project Size and System Size

An application is built up by a series of projects over a period of time. Some of the projects may change or delete functionality already in the system. The changed or deleted functionality needs to be included in the project count but not necesarily in the application count.

The Function Point Counting Process

Lalcrest uses a standard process to count Function Points: Function Point Counting Process

Count Correctness

• Using Function Point Workbench ensures rules are followed. Function Point Workbench

• Using Function Point Workbench ensures arithmetic correctness

• Lalcrest recommends that only IFPUG certified counters are used