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DAT 601 - Robin Le Couteur - 3/23/2018

Friday, March 23, 2018

ER Modelling Continued pt.2

Today we covered more ER modelling concepts

Enhanced ER Modelling

We had a look at EER modelling, here is some of the rules and how they can be used:

Union Types

Union Type or Category
The Idea of unions is to show how entities can have categories and types.
  • U - Categorical or union
  • D - The relationship between sub class and super class is denoted with the D symbol. Sub class is a type of the generalized super class. Here is an example of how a Shape super class has different  types or sub classes. The Super class can be one of the subclasses
  • O - Overlap. Can be one or many of the different options

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