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Chapter 7.3: Data Modeling for the Structured Environment



















































               Fig. 7.3.1 Separating detailed and summarized data.


           After the granular data are identified, the next step is to “abstract” the data. The data are
           abstracted to its highest meaningful level. The highest meaningful level is called an entity.


           As a simple example of abstraction, suppose a corporation has female customers, male
           customers, foreign customers, corporate customers, and governmental customers. The

           data model creates the entity known as “customer” and wraps all of the different types of
           customer together.


           Or suppose the company produces sports cars, sedans, SUVs, and trucks. The data model
           abstracts the data into the entity—vehicle.


           The ERD

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