Guideline for Converting Software Size to Cost Estimation from Sequence Diagram Using COSMIC Function Points

Abstract

This study explores the application of the early COSMIC method—a functional size measurement approach designed for early-stage software development—by leveraging sequence diagrams as primary input artifacts. Unlike COSMIC as comprehensive size functional measurement, early COSMIC only indicates the software pre-size estimation when system specifications are incomplete, making it well-suited for iterative development. The method was implemented in a case study involving the development of pond applications using IoT sensors, which comprised a unified modelling language (UML) sequence diagram. Its functional size was estimated at 45 COSMIC Function Points (CFP), derived from the classification of data movements such as Entry, Read, Write, and Exit. Based on the calculated functional size and labor pay rates (refer to Inkindo billing rates), the projected development cost for the application was IDR 109,361,574 allocated then. These findings affirm that early COSMIC provides a systematic and practical contribution for software project manager in real-world project development budget estimation.