Db8 Petrie

Chapter 8: Structuring System Data Requirements

Petrie Case Questions

1. Review the data-flow diagrams you developed for questions in the Petrie Electronics case at the end of Chapter 7 (or diagrams given to you by your instructor). Study the data flows and data stores on these diagrams and decide whether you agree with the team’s conclusion that the only 7 entity types needed are listed in the case and in PE Figure 8-1. If you disagree, define additional entity types, explain why they are necessary, and modify PE Figure 8-1 accordingly.

2. Again, review the DFDs you developed for the Petrie Electronics case (or those given to you by your instructor). Use these DFDs to identify the attributes of each of the six entities identified in your answer to Question 1. Write an unambiguous definition for each attribute. Then, redraw PE Figure 8-1 by placing the six (and additional) entities in this case on the diagram along with their associated attributes.

3. Using your answer to Question 3, draw the relationships between entity types needed by the system. Remember, a relationship is needed only of the system wants data about associated entity instances. Give a meaningful name to each relationship. Specify cardinalities for each relationship and explain how you decided on each minimum and maximum cardinality on each end of each relationship. State any assumptions you made if the Petrie Electronics cases you have read so far and the answers to questions in these case do not provide the evidence to justify the cardinalities you choose. Redraw your final E-R diagram in Microsoft Visio.

4. Now that you have developed in your answer to Question 4 a complete E-R diagram for the Petrie Electronics database, what are the consequences of not having an employee entity type in this diagram? Assuming only the attribute be moved from the entity it is currently associate with to an employee entity type if it were in the diagram. Why or why not?

5. Write...