©Net Objectives, 2002
NetObjectives
63
Use Cases to Estimate Budget
nOne use case
n= 3-9 steps in Main Success Scenario (MSS)
nMSS = 3-7 Unfolded Tasks (data, UI, logic, infrastructure…)
nEach step of MSS has 1-3 alternatives
nOne alternative = 1-5 Unfolded Tasks
n
nSo, one use case = 5 + 6x2x3 = 41 Tasks
nOne Task = 1-4 days of effort
nSo, one use case = 41x2.5 = 100 days of effort
n
nYour Mileage May Vary
I use the terms “story” here to tie into XP. If you use XP practices to develop these stories you have a built in set of documentation on how to do this – the XP library.

Each organization must determine its own “magic constants” for estimation – it will take a couple of projects to do this…  You can also look at a couple of previous projects, and count the use cases found in the system (this is fairly easy) and compare it to the actual cost to develop it. Then use Yesterday’s Weather to determine how much to budget for each use case. Then run with it as if it were true until it proves not to be…

Numbers: 5 TTs in MSS, 6 steps in MSS, 2 alternatives per step, 3 TTs per alternative

For example, in XP we would Use Story which further decomposes to Engineering Task…