IFPUG function points is the most commonly used sizing method. It is better suited to applications that contain user interface, reports and databases.
With IFPUG, function points are assigned to a screen/report (depending on the number of data elements on the screen/report) and the number of database tables that are referenced. Function points are also assigned to tables depending on their size.
The total is the unadjusted function point count (UFP). There is then an adjustment to cater for the other attributes that need to be considered when developing an application. Currently there are 14 attributes to assess. For details on function point counting the go to IFPUG.
Not every size method is ISO certified. IFPUG, FiSMA, Mark II, Cosmic and NESMA are ISO/IEC certified standard for functional size measurement.