Entity modeling is a way of graphically representing a database's design, which organizes the tables that hold user data. Making entity relationship (ER) models (also called ER diagrams) isn't difficult; you just have to practice. You can group ER diagrams into categories that represent sales, scheduling, reservations, asset management, inventory control, and so on. And you can represent each category with a template ER diagram, or metamodel. Just as we define metadata as "data about data," in this article we can define "metamodel" as a "model of models."

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