Create an ER diagram for the following enterprise.

The first entity set is Studios. The only information of interest that you need to keep is its name, address, and website URL. It may seem that the name and address as are a key, but in this era of multinational companies, an address can be difficult to pin down, but every company has a website. Further, although many companies have multiple domain names (http://motorola.com or http://mot.com/), there is generally only one domain that they use in advertising or put on their Annual Report, so that is the domain that would serve as the key.

The Series entity set is uniquely identified by Title and Creator, since it is possible that two Series were created with the same name, but very unlikely with the same creator (an all Star Trek series have different subtitles). Other attributes include: Website, Start date, and End date.

Next, there is a Produces relationship between Studios and Series. A studio may produce many tv series, but a given series is produced by a single studio.

There is relationship Starring between Series and Actors. There can be many actors in a series, and an actor can be in many different series.

Characters have two attributes: Name and Title/Role.

There is a relationship from Series to Characters and another one to Episodes. A series has many characters as well as many episodes. A character is uniquely defined by both his/her name AND associated series, especially because multiples series can have the same character name. The same argument is true about Episodes (that is, an episode can be uniquely identified by its title AND the title of the series).

There is a relationship between Episodes and Characters because it is helpful to know which characters were featured in a given episode, especially for an ensemble cast like Star Trek.

There is relationship between Actors and Characters (an actor can play multiple characters and a character can be played by multiple actors).

A note about the Episodes entity set: you can assume for the data that is modelled that every episode had a unique title within a series. Other attributes include: Season, Air Date, Quality Rating, Description, and URL.

Finally, all actors register with the Actors Guild, so that screen names are essentially unique. The only other attribute of Actors is Website.

This question deals with the airline database entity-relationship diagram shown in Figure 1 below.

  

Figure 1: Airline database

Extend this E-R database design to include catering data, i.e., meal service.

• A meal is associated with a set of dishes, and has a unique Meal_Id attribute.
• A dish has a name, cost and fat content.
• Each flight is associated with at most one meal.
• Each meal is cooked by a single cook who is an employee.

This question deals with the department store entity-relationship diagram shown in Figure 2 below.

  

Figure 2: Department store E-R design.

(a) For each entity set, define a primary key. Justify your choice in each case in a sentence or two.

(b)Which, if any, of the entity sets should be weak? Justify your answer in a sentence or two.

(c)Explain the purpose of the descriptive attribute date in the placed_by relationship. Explain the effect of including it, or not, in the primary key of order. Similarly, explain the effect of including it, or not, in the primary key of customer.