Modeling does not require so much
There are claims that ER modeling on the basis of extended ER models offers opportunities which are not necessary. This claim is true if the application is very simple. Usually examples discussed in textbooks are simple. For this reason, the reader has the impression that he/she knows how to model any application looking over such simplistic examples. Reality, however, is far richer. Thus, modelers meet applications which cannot be handled on the basis of simple models. It is better to use a model with opportunities which might be used if the applications requires so. The opportunities should be disselectable whenever there is no need in those.
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