The function point measure of the functional size of a software set is well known for its use as an input in the estimation of development effort. The authors devised a unified modeling language (UML) model-based approach. This paper introduces a technique to reliably count function points (FPs) from UML models, in accordance with standardized International Function Point Users Group (IFPUG) rules, and without employing a certified counter. The goal of the approach is to improve the process of measuring FPs, and to that end the paper presents mappings between FP elements and UML language constructs. Among the strengths of the paper are clear examples illustrating modeling and counting rules, and an initial empirical validation complemented by an industrial application of the approach.

The approach is model based, as it requires a precise model of requirements obtained using measurement-guided UML modeling. The measurement requirements are essentially homogeneity of models and explicit coverage of all required FP elements. The approach is superior to a posteriori techniques where FP is applied to UML models built without attention to measurement needs. In the central section of the paper, “Measurement-oriented UML Modeling,” using Gym IS case study fragments, the authors explain seven rules about how a UML model of the system to be measured is to be built, and one rule explaining how to count FPs from such models. The following UML diagrams, constrained by the rules, are required: use case, collaboration, class, and sequence. The rules do not extend UML notation, nor do they require information not usually available in detailed UML models. In conclusion, this paper points out that measurement and modeling are not independent, as changes in the model do change its FP count.

The paper is recommended to developers and students already familiar with FPs, and interested in using UML models to calculate FPs.