Effort Estimation based on Use Case Points

Question

As of now I have done effort estimation based on experience and recently using function points.

I am now exploring UCP, read this article http://www.codeproject.com/KB/architecture/usecasep.aspx. I then checked various other articles based on Use Case Points (UCP). I am not able to find out how exactly it works and is it correct.

For example, I have a login functionality where user provides userid and password and I check against a table in database to allow or deny login. I define a user actor and Login as a Use Case.

As per UCP I categorize Login use case as Simple and the GUI interface as Complex. As per UCP factor table I get 5 and 3 so the total is 15. After applying the technical factor and environmental factor adjustment it becomes 7. If I take productivity factor as 20 then I am getting 140 hours. But I know it will take at most 30 hrs along with documentation and testing efforts.

Am I doing something wrong in defining the Use Case here? UCP says if the interface is GUI then its complex but here the gui is easy enough so should I downgrade that factor? Also factor for simple is 5, should I define another level as Very Simple? But then am I not complicating the matter here?

Answer 1

Ironically, the prototypical two box logon form is much more complicated than a 2 box CRUD form because the logon form needs to be secure and the CRUD form only needs to save to a database table (and read and update and delete).

A logon form needs to decide if where to redirect to, how to cryptographically secure an authentication token, if and how to cache roles, how to or if to deal with dictionary attacks.

I don't know what this converts to in UCP points, I just know that the logon screen in my app has consumed much more time a form with a similar number of buttons and boxes.

Last time I was encouraged to count function points, it was a farce because no one had the time to set up a "function points court" to get rulings on hard to measure things, especially ones that didn't fall neatly into the model that function point counting assumes.

Answer 2

Here's an article talking about Use Case Points - via Normalized Use Case. I think the one factor overlooked in your approach is the productivity which is suppose to be based on past projects. 20 seems to be the average HOWEVER if you are VERY productive (there's a known 10 to 1 ratio of moderate to good programmers) the productivity could be 5 bringing the UCP est. close to what you think it should be. I would suggest looking at past projects, calculating the UCP, getting the total hours and determining what your productivity really is. Productivity being a key factor needs to be calculated for individuals and teams to be able to be used in the estimation effectively.

Answer 3

Part of the issue may be how you're counting transactions. According to the author of UCP, transactions are a "round trip" from the user to the system back to the user; a transaction is finished when the system awaits a new input stimulus. In this case, unless the system is responding...a logon is probably just 1 transaction unless there are several round trips to and from the system.

Check out this link for more info...

http://www.ibm.com/developerworks/rational/library/edge/09/mar09/collaris_dekker/index.html