5+-+Advanced+Data+Modeling

5+-+Advanced+Data+Modeling - AdvancedDataModeling...

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Advanced Data Modeling Douglas Havelka Miami University
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EERM Extended or Enhanced To capture more real world information
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Supertypes and Subtypes Categories, classes, types Avoids nulls More detailed, accurate specification of  relationships Animal Mammal Bird
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Entity Supertype Generic abstract type that is related to >1  subtype A generalization Has attributes common to all subtypes
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Specialization Hierarchy SEE PICTURE All 1:1 “Is-A” relationships Employee Accountant Pilot Mechanic
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Inheritance Allow the subtype instances to inherit all  the attributes of the supertype Primary key is inherited
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Subtype Discriminator The attribute in the supertype that  determines, indicates, the subtype of the  instance Employer-Type Animal-Type Gender
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Disjoint Constraint Disjoint Non-overlapping Unique subset of superset Each instance can only be 1 subtype
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5+-+Advanced+Data+Modeling - AdvancedDataModeling...

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