1. Consider the E-R diagram in Figure 7-20. Based onthis E-R diagram, answer the following questions:
a. How many EMPLOYEES can work on aproject?
One-to-many employees
b. What is the degree of the Used_on relationship?
2, since there are two entity types participate in this relationship
c. Do any associative entities appear in this diagram? If so, name them.
No
d. How else could the attribute Skill be modeled?
The attribute Skill is a multivalued one.
e. What attributes might be attached to theWorks_on relationship?
We could attach the following attributes:
1. FROM: From which date employee works on the project
2. PCT: How much of his time does he use in working on this project
f. Could TOOL be modeled as an associativeentity? Why or why not?
No, because Used_on relationship shows that each task has one and only one tool. No additional data is required.
2. The owner of two pizza parlors located in adjacent towns wants to computerize and integratesales transactions and inventory managementwithin and between both stores. The point-of-salecomponent must be easy to use and flexibleenough to accommodate a variety of pricingstrategies and coupons. The inventory management, which will be linked to the point-of-salecomponent, must also be easy to use and fast.The systems at each store need to be linked sothat sales and inventory levels can be determinedinstantly for each store and for both stores combined. The owner can allocate $40,000 for hardware and $20,000 for software and must have thenew system operational in three months. Training must be short and easy. Briefly describe threealternative systems for this situation and explainhow each would meet the requirements and constraints. Are therequirements and constraintsrealistic? Why or why not?
a. Alternative A: ABC company is a well-known IT services firm with an over a decade history. ABC offers to utilize the project using an already used successfully package of software that will be installed on new hardware ordered by an outsourcing associate hardware vendor. Four months and $250,000 ($200,000 for software and $50,000 for hardware) will be needed.
b. Alternative B: XYZ company is a local company that offers open-source solutions with a non-significant contribution for training users in their products. XYZ has utilized a similar project, that can be modified by experienced programmer if needed.
c. Alternative C: 123 company offers cloud computing services for low cost and high performance. All software is on vendor's side, running on his computer systems. The system will be running on 24/7 and users will be able to access it even from home. $150,000 and 6 months will be required for an all-in-one solution.
In my opinion, thiw project is underestimated. I believe that $60,000 for this project is too little. Moreover, three months is a short period time if we think of all the software development phases and the training sessions that will take place at the end. Alternative C seems to be the most appropriate for the case, since it has a lower budget than XYZ, even it will need 2 extra months. Moreover, being on cloud, will be more flexible for our company to migrate to something else in the future.
3. Compare the alternative systems from Problemand Exercise 2 using the weighted approachdemonstrated in Figure 7-19. Which systemwould you recommend? Why? Was the approachtaken in this and Problem and Exercise 16 usefuleven for this relatively small system? Why orwhy not?
Judging by the weighted approach, I would prefer Alternative C (123 company), which has the best score (424). It seems that even for small projects, it is useful to approach the project assignment in many different ways. For example we see in the diagram that Alternative A's score (408) isn't much less than Alternative C's and maybe a second thought over ABC's proposal shall be made.