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Data Modeling Made Simple with ER/Studio Data Architect by Steve Hoberman

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The following statements can be made about the business rules, based on the role names specified in the relationships in ER/Studio. The role names are shown in italics.

Each Employee may process one or many Transactions.

Each Transaction must be processed by one Employee.

Each Transaction must be either an Order, a Credit, or a Debit.

Each Order is a Transaction.

Each Credit is a Transaction.

Each Debit is a Transaction.

Each Employee may contact one or many Customers.

Each Customer must be contacted by one Employee.

Each Customer may place one or many Orders.             

Each Order must be placed by one Customer. ...

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