Solution

Function Point Based Metrics (Albrecht, 1979 - IBM)

Purpose: Measure functionality from user view, independent of language.

Steps:

1. Count 5 Function Types:

   • EI (External Inputs) ×4
   • EO (External Outputs) ×5
   • EQ (External Queries) ×4
   • ILF (Internal Logical Files) ×10
   • EIF (External Interface Files) ×7
     (Weights for Average complexity - also Low/High variants)

2. Unadjusted FP (UFP) = Σ count×weight

3. Value Adjustment Factor (VAF) = 0.65 + 0.01× Σ Fi, where Fi = 14 General System Characteristics (0-5 each): data comm, performance, etc.

4. FP = UFP × VAF

Example:

• EI 10×4=40, EO 5×5=25, EQ 4×4=16, ILF 2×10=20, EIF 1×7=7 → UFP=108
• Σ Fi = 35 → VAF=1.0 → FP=108

Metrics derived:

• Productivity = FP/PM
• Quality = Defects/FP
• Cost = Cost/FP

Advantage over LOC: language-independent, early estimation from SRS.