this technique smell a lot to function points
Indeed it does. Karner, who did the original work on this as a thesis, attempted to move the function point style of estimation backwards in the design lifecycle to get an early estimate of size given just the use case and actor model.
IOW function points are excellent estimators given that the entire process is followed - this means you essentiallty cant do it until you have a conceptual system design.
Since estimates are usually needed way back at the initial scoping exercises, the point where use case approaches exhibit their greatest power, he analysed a small set of projects and proposed the UCP method.
Similar to FPC, its basis is to get some metric on overall size and convert that to an effort estimate given technical approach and environmental risk modifiers - TCF and ECF.
My basic problem with the UCP method (as opposed to FP counting) is that Karner's original constants are still used without question. Given the small sample set he based it on, I would have thought that the IT and academic communities would, by now, have reviewed and revised those constants. I have seen some evidence of the TC constant being quoted as .65 rather than .6 as Sparx has implemented but I have no reference to back that up.
(one thing about the EA UCP model that irks me is that you cannot persist your own values for TWF,TC,EWF and EC as I find that, for example, a TC and EC of .65 gives me a better IMO estimate for test effort - but thats another matter)
Karners original work does not appear to be published on the net, but "Estimating Object-Oriented Software Projects with Use Cases" by Kirsten Ribu (MSc Thesis 2001 University of Oslo, Department of Informatics) is obtainable and gives some excellent insights. I'm sorry, I dont have the link for it, though...
hth
Bruce
p.s. Ribu quotes Schneider and Winters. Applying use Cases. Addison-Wesley, 1998. as a basis reference for Karners work - but I haven't seen this work.
