Week 6_Petrie's Electronics Cases Closeout_ESSAY

Week 4 Chapter 7 Petrie’s Electronics Case Questions Grading Rubric

Petrie’s Electronics Case Questions Solutions (15 Points)

2. Again, review the DFDs you developed for the Petrie’s Electronics case (or those given to you by your instructor). Use these DFDs to identify the attributes of each of the six entities listed in this case plus any additional entities identified in your answer to Question 1. Write an unambiguous definition for each attribute. Then, redraw Figure 7-1 by placing the six (and additional) entities in this case on the diagram along with their associated attributes. (5 points)

Answers will vary, I suggested List at least 2 attributes for each of the six entities and describe then in a short sentence or bullet statement.  Then redraw PE Fig 7-1 to look like figure 7-21 on page 223.

3. Using your answer to Question 2, designate which attribute or attributes form the identifier for each entity type. Explain why you chose each identifier.

(5 points)

Answers will vary, Look at page 199 for the definition of an identifier – an attribute that will make each entity unique (sometimes called candidates Key or primary keys; ie student ID etc).  Pick an identifier for each of the six entities that will make them unique. Identifiers are underlined in attribute list in entities – so look on pages 200-201 for some examples)

4. Using your answer to Question 3, draw the relationships between entity types needed by the system. Remember, a relationship is needed only if 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’s Electronics cases you have read so far and the answers to questions in these cases do not provide the evidence to justify the cardinalities you choose. Redraw your final E-R diagram in Microsoft Visio. (5 points)

Answers will vary, I suggested Use the DFD on page 187, then add the relationships like in figures 7-20 and 7-21 on page 223.  Example is promotion_is_earned would be the relationship between customer and promotion…what about the rest?

Make sure you validate the cardinality for each relationship; for instance customer does not have a cardinality for coupons or transactions in PE figure 7-1 on page 230 – should you add some?