The following questions were adapted from Rob, P. & Coronel, C. (1997) Database Systems: Design, Implementation, and Management. Cambridge, MA: Course Technology. This book is on reserve at the FIMS library. I recommend that you read pages 226-233 and work through the example on pages 255-256. Make sure you fully understand the examples and resultant ER diagrams before proceeding with the following questions.

1. Use the following business rules to write all appropriate connectivities and cardinalities in an E-R diagram:

• A department employs many employees, but each employee is employed by one department.
• Some employees, known as "rovers", are not assigned to any department.
• A division operates many departments, but each department is operated by one division
• An employee may be assigned to many projects and a project may have many employees assigned to it.
• A project must have at least one employee assigned to it.
• One of the employees manages each department.
• One of the employees runs each division.

2. The Hudson Engineering Group (HEG) has contacted you to create a conceptual model whose application will meet the expected database requirements for its training program. The HEG administrator gives you the following description of the training group's operating environment:

Given this information, do the following:

• Draw the E-R diagram for HEG.
• Describe the relationship between instructor and course in terms of connectivity, cardinality, and existence dependence.

3. Given the following business rules, create the appropriate E-R diagram for each of the specified relationships:

• A company operates four departments.
• Each department in part (a) employs employees.
• Each of the employees in part b may or may not have one or more dependents.
• Each employee in part (c) may or may not have an employment history.

4. The Jonesburgh County Basketball Conference (JCBC) is an amateur basketball association. Each city in the county has one team that represents it. Each team has a maximum of twelve players and a minimum of nine players. Each team also has up to three coaches (offensive, defensive, and PT coaches.) Each team plays two games (home and visitor) against each of the other teams during the season. Given these conditions, do the following:

• Identify the connectivity of each relationship.
• What type of dependency exists between CITY and TEAM?
• What is the cardinality between teams and players? Between teams and city?
• What is the dependency between coach and team? Between team and player?
• Draw the E-R diagram to represent the JCBC database.

5. Create an ER Model for the following:

• An INVOICE is written by a SALESREP. Each sales representative can write many invoices, but each invoice is written by a single sales representative.
• The INVOICE is written for a single CUSTOMER. However, each customer may have many invoices.
• An INVOICE may include many detail lines (LINE) which describe the products bought by the customer.
• The product information is stored in a PRODUCT entity.
• The product's vendor information is found in a VENDOR entity.