An article by DavidLongstreet at SoftwareMetrics. http://www.softwaremetrics.com/Articles/usecases.htm

The author describes some techniques for doing FunctionPointAnalysis using UseCases as the source of requirements.  Longstreet argues that it makes a good match.  The section on sizing a UseCase is interesting in how it reflects thinking similar to XP's process of sizing EngineeringTask and UserStories in the PlanningGame.  Interestingly, his rule of thumb of "no more than 50 FunctionPoint''''''s per Use Case", means, taking an industry average of 20 hours/FunctionPoint, a single UseCase could be up to 25 weeks of work and still not be considered too large. If that seems way out of line, suspect the figure for hours/FunctionPoint as an order of a magnitude too large.

--StevenNewton