Functional versus Design Measures for Model-Driven Web Applications: A Case Study in the Context of Web Effort Estimation

In the literature we can identify two main approaches for sizing model-driven Web applications: one based on design measures and another based on functional measures. Design measures take into account the modeling primitives characterizing the models of the specific model-driven approach. On the other hand, the functional measures are obtained by applying functional size measurement procedures specifically conceived to map the modeling primitives of the model-driven approach into concepts of a functional size measurement method. In this paper, we focus our attention on the Object-Oriented Hypermedia (OO-H) method, a model-driven approach to design and develop Web applications. We report on the results of an empirical study carried out to compare the ability of some design measures and OO-HFP (a model-driven functional size measurement procedure) to predict the development effort of Web applications. To this aim, we exploited a dataset with 30 Web projects developed using OO-H. The analysis highlighted that each design measure was positively correlated with the Web application development effort. However, the best estimation model obtained by exploiting the Manual Stepwise Regression employed only the measure Internal Links (IL). Furthermore, the study highlighted that the estimates obtained with the IL based prediction model were significantly better than those achieved using the OO-HFP based prediction model. These results seem to confirm previous investigations suggesting that Function Point Analysis can fail to capture some specific features of Web applications