Hacaloglu,T.Unlu,H.Demirors,O.Abran,A.Information Systems Engineering2024-10-062024-10-06202001613-0073[SCOPUS-DOI-BELIRLENECEK-54]2-s2.0-85098219881https://hdl.handle.net/20.500.14411/9531Functional size has been used in software engineering for more than 40 years. When measured early in the software development life cycle, it can serve as direct input for effort estimation. The COSMIC Functional Size Measurement (FSM) method developed by the Common Software Measurement Consortium (COSMIC) is the latest ISO-compliant functional sizing method. A streamlined manual titled ''Software Development Velocity with COSMIC Function Points'' summarizes the measurement process and shortens the learning time. The aim of this study is to compare the classic COSMIC FSM manual and this new “light” manual in terms of accuracy of the resulting FSM applied to case studies. The findings show that use of the light manual results in accurate measurement. In addition, there were no significant time differences between the two. With respect to the variations in COSMIC Function Points (CFP) values in the two case studies, they three causes were identified: the Object of Interest (OOI) concept and corresponding data groups, details regarding Functional Process Independence, and Error/Confirmation messages related to the scope of the information included in the manuals. Copyright © 2020 for this paper by its authors.eninfo:eu-repo/semantics/closedAccessCOSMICFunction pointsISO 19761SizeSoftware measurementConference ObjectN/AQ42725