Entity-relationship Model and E-r Diagram
Week 4 Problems and Exercises
Chapter 7 5) Consider the E-R diagram in Figure 7-20. Based on this E-R diagram, answer the following questions:
a. How many EMPLOYEES can work on a project? There is no set limit of employees to work on one given project. b. What is the degree of the Used on relationship? There are 2 degrees for the Used on relationship.
c. Do any associative entities appear in this diagram? If so, name them. Yes there is task which is an associative entity.
d. How else could the attribute Skill be modeled? As a square attached back to Task.
e. What attributes might be attached to the Works on relationship?
f. Could TOOL be modeled as an associative entity? Why or why not?
16) The owner of two pizza parlors located in adjacent towns wants to computerize and integrate sales transactions and inventory management within and between both stores. The point-of-sale component must be easy to use and flexible enough to accommodate a variety of pricing strategies and coupons. The inventory management, which will be linked to the point-of-sale component, must also be easy to use and fast. The systems at each store need to be linked so that sales and inventory levels can be determined instantly for each store and for both stores combined. The owner can allocate $40,000 for hardware and $20,000 for software and must have the new system operational in three months. Training must be short and easy. Briefly describe three alternative systems for this situation and explain how each would meet the requirements and constraints. Are the requirements and constraints realistic? Why or why not?
17) Compare the alternative systems from Problem and Exercise 16 using the weighted approach demonstrated in Figure 7-19. Which system would you recommend? Why? Was the approach taken in this and Problem and Exercise 16 useful even for this relatively small system? Why or why