Sunday, March 9, 2014

How to model a ternary associative entity with a binary constraint? | LinkedIn Group: Data Modeling

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My comment 

Based on the information provided (and including your later remark that this is just a hypothetical conceptual model to help illustrate a concept), Option A shows the right model.

Additional relationships as of your options B and C are redundant since they do not add any semantics to the model that are not already expressed in Option A. Practical test: If you generate foreign keys, the model as of Option A will look as shown at (using the notation "Information Engineering +"). 

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The foreign keys in the table Diploma still allow a direct navigation to the table University and the table Degree (and vice versa).