Unadjusted Function Points - Practices

Each function point count is multiplied by the numerical rating derived from the above table(s) to determine the complexity rated value. The complexity rated values on each row are summed across the table. This gives the total value for each type of component. The totals for all the components are then summed up to arrive at the total number of Unadjusted Function Points or UAF.

Value Adjustment Factor:

The Value Adjustment Factor (VAF) is based on fourteen General System Characteristics (GSC's). The degrees of influence range on a scale of zero to five, from no influence to strong influence. The GSCs are listed below:

1. Data communication
2. Distributed functions
3. Performance objectives
4. Heavily used configuration
5. Transaction rate
6. Online data entry
7. End-user efficiency
8. Online update
9. Complex processing
10. Reusability
11. Installation ease
12. Operational ease
13. Multiple sites
14. Facilitate change 

VAF = 0.65 + (Sum of degrees of Influence of the fourteen GSCs)/100

The final Function Point Count is obtained by multiplying VAF by the Unadjusted Function Point (UAF).

FP = UAF * VAF

Summary:

Function points, as discussed earlier, can be used to size software applications accurately, as sizing is an important factor in determining productivity. Since function point has a unique and consistent method, different people measuring them will give almost the same result with very little margin of error. A non-technical person can easily understand function points, which helps in communicating the same to the end-user effectively and easily.

Glossary of Terms:

DET Data Element Type
EIF External Interface File
EI External Inputs
EO External Outputs
EQ External Inquiries
FTR File Types Referenced
GSC General System Characteristics
ILF Internal Logical Files
UAF Unadjusted Function Point
VAF Value Adjustment Factor