3 replies to this topic

[seristee]

I am a second year software engineering student and i need some help understanding entity relationships. this is the assignment ...

VideoCity Case Study:
A video rental company VideoCity, has several branches throughout the UK. The data held on each branch is the branch address made up of street, city, state, and zip code, and the telephone number. Each branch is given a branch number, which is unique throughout the company. Each branch is allocated staff, which includes a Manager. The Manager is responsible for the day-to-day running of a given branch.
The data held on a member of staff is his or her name, position, and salary. Each member of staff is given a staff number, which is unique throughout the company. Each branch has a stock of videos. The data held on a video is the catalog number, video number, title, category, daily rental, cost, status, and the names of the main actors, and the director. The catalog number uniquely identifies each video. However, in most cases, there are several copies of each video at a branch, and the individual copies are identified using the video number.
A video is given a category such as Action, Adult, Children, Drama, Horror, or Sci-Fi. The status indicates whether a specific copy of a video is available for rent. Before hiring a video from the company, a customer must first register as a member of a local branch.
The data held on a member is the first and last name, address, and the date that the member registered at a branch. Each member is given a member number, which is unique throughout all branches of the company. Once registered, a member is free to rent videos, up to maximum of ten at any one time.
The data held on each video rented is the rental number, the full name and number of the member, the video number, title, and daily rental, and the dates the video is rented out and date returned. The rental number is unique throughout the company.
Tasks:
(a) Identify the main entity types of the video rental company.
(14 marks)
(b) Identify the main relationship types between the entity types described in (a) and represent each relationship as an ER diagram.
(14 marks)
© Determine the multiplicity constraints for each relationship described in (b). Represent the multiplicity for each relationship in the ER diagrams created in (b).
(16 marks)

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(d) Identify attributes and associate them with entity or relationship types. Represent each attribute in the ER diagrams created in ©.
(12 marks)
(e) Determine candidate and primary key attributes for each (strong) entity type.
(16 marks)
(f) Using your answers (a) to (e) attempt to represent the data requirements of the video rental company as a single ER diagram. State any assumptions necessary to support your design.
(18 marks)

Please can anyone help me in answering these questions. i think i have the first answer

(a). The main entity types of the video rental company are:
1. Branch
2. Staff
3. Videos
4. Member
5. Category
6. Rented Video


Thanks in advance

Edited by seristee, 23 October 2011 - 11:06 AM.

[Orjan]

To identify entities, see if it is some kind of unit and not a parameter to a unit. it is usually nouns or verbs, and not adjectives. I'd say that you're in the right direction, but still not all there. I think you have one in your list that isn't an entity, and that you are missing two entities. The one I think you've got wrong could be rephrased into a better name of the entity.

[seristee]

oh k thanx im guess its the rented video one it should be something like VideoForRent

[Orjan]

Yes. I think that would be an more appropriate name. For (b), see how these entities connect together, as in 1-to-1, 1-to-many or many-to-many. also try name the relation between the entities. as if it was list of cars and owners, I could write something like this: "one car is owned by an owner, and an owner owns cars". This can also be expanded to answer © if done correctly.