Since Chen published the E/R model in 1976, some proposals extending its expressive power have appeared, some of them are based in the preceding semantic models. Thus, currently, some conceptual models allow relationships between relationships and even generalizations of relationships. These proposals could be better understood if relationships are considered as object types allowing other possibilities as, for example, aggregation of relationships. In this chapter, using a modeling example, we will discuss about the benefits of this approach, mainly about the possibility to model simpler conceptual schemata. We also present an empirical study for proving if modeling with relationships between relationships is more difficult than not use them for novice designers. As a result of this study, it seems that complexity is not affected by the kind of modeling selected.
An Empirical Study on the Scalability of Selective Mutation Testing
