VDD vs Function Points
Function Points, introduced by Allan Albrecht at IBM in 1979 and further developed by IFPUG and COSMIC, measure software size from the user's perspective. VDD shares the conviction that size should be counted, not guessed, and builds a delivery and pricing method around it.
At a glance
Dimension
VDD
Function Points
What is counted
Engineering artifacts in 12 categories, including test cases, data migrations and environment setup
Functional user requirements: inputs, outputs, inquiries and data files
Verification effort
Counted: Test Case Bricks and Independent Verification Effort
Not counted. Size only
Price basis
Base Unit Rate per category, calibrated on the organization's own history
Outside the method. Some contracts negotiate a price per Function Point
Who counts
The tech lead, per user story
Usually trained or certified counters
Acceptance
Independent Verification Gate
Outside the method
Forecast
P50/P85 from weekly throughput
Outside the method
Main purpose
Estimate, price, accept and forecast delivery
Measure functional size and benchmark productivity
Why it changed
Function Points proved that software size can be measured independently of the technology used to build it. VDD keeps that lesson.
What VDD adds is the part AI made decisive: verification. When code is cheap to generate, the cost sits in checking it. So VDD counts test cases as Bricks, measures the verification effort of each category, and does not count a Unit as delivered until someone who did not build it confirms it.
How the concepts map
Function Points
VDD
Function Point count
Brick count by category
Productivity (hours per Function Point)
Base Unit Rate (money per Brick, per category)
Counting by functional requirement
Counting per user story: one Delivery Unit
No equivalent
Independent Verification Gate
No equivalent
P50/P85 delivery dates
Questions
Is VDD a Function Point method?
No. It belongs to the same family of counted estimation, but it counts engineering artifacts and their verification, not functional size.
Can we use both?
Yes. Function Points can stay your benchmark of functional size; VDD prices, accepts and forecasts the delivery.