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Unadjusted Function Points - Practices

Function Point Analysis is a structured technique of classifying components of a system. It is a method used to break systems down into smaller components so that they can be better understood and analyzed. Function Point Analysis provides a structured technique for problem solving.

TABLE OF CONTENTS:
  1. An Overview of Function Point Analysis
  2. The Five Major Components
  3. Rating and Ranking the Components
  4. Unadjusted Function Points
By: Nandini Venugopalan
Rating: starstarstarstarstar / 107
June 02, 2004

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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.

Component TypeComponent Complexity
LowAverageHighTotal
External Inputs__* 3=EI1__* 4=EI2__* 6=EI3

EI1+EI2+EI3

External Outputs__* 4=EO1__* 5=EO2__* 7=EO3EO1+EO2+EO3
External Inquiries__* 3=EQ1__* 4=EQ2__* 6=EQ3EQ1+EQ2+EQ3
Internal Logical Files__* 7=ILF1__* 10=ILF2__* 15=ILF3ILF1+ILF2+ILF3
External Interface Files__* 5=EIF1__* 7=EIF2__* 10=EIF3EIF1+EIF2+EIF3
Total UAF(EI1+EI2+EI3) + (EO1+EO2+EO3) + (EQ1+EQ2+EQ3) + (ILF1+ILF2+ILF3) + (EIF1+EIF2+EIF3)

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



 
 
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