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Object-Role Modeling Fundamentals by Terry Halpin

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NORMA Lab 4

Figure 4.36 A Visio diagram of an ORM schema to be entered in NORMA

Figure 4.36 shows an ORM schema that illustrates most aspects of the ORM graphical notation introduced in this chapter. The fact type Course is a prerequisite of Course stores only direct prerequisites, so is acyclic and strongly intransitive. The external frequency constraint was discussed earlier. The 2..5 frequency range constraint ensures that if we record any workers for a given project we must record at least 2 and at most 5 students for this work. The value-comparison constraint ensures that a project cannot end before it starts. The role cardinality constraint ...

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