CIT 381 Database Systems
Fall 2007

Please do this work yourself. While we encourage you to have discussions with your fellow students, such interaction should be at a high-level. You must be able to complete the details of the homework on your own.

Your ER diagrams can be either done by hand or generated by ER Studio.

1. (15 points) Look on the web for definitions of the following terms. Try to put the answers in your own words.
   1. weak entity
   2. primary key
   3. foreign key
   4. entity intgrity
   5. referential integrity

2. (10 points) Draw an ER diagram for the following problem.
   
   A shipping company maintains a list of its crew and its ships. Each crew member has a crewId, status, first and last name, and address. Each ship has a shipRegNumber (the key), shipTonnage, and shipAge. A crew member is assigned to a ship, where he/she works. It's possible for a crew member to work on no ship, but not possible to work on two or more. Furthermore, each ship has exactly one crew member assigned to it as a captain.
   

3. (15 pts) Draw an ER diagram for the following problem.
   
   An auction web site has items for sale that are provided by sellers. Each item has an opening price, a description, and an ending time. Customers submit bids. The highest, earliest bid submitted before the ending time is the winning bid and the item is sold to the bidder. Each seller must pay the auction company 5% of the winning bid. The auction company wants to be able to analyze the sales behavior of its customers and sellers and so must keep track of all bids and sales. (Hint: the entities look like they'll be customers, sellers, items, and bids.)
   

4. (15 pts) A researcher at the UO wants to collect journals, papers, and the authors of those papers before embarking on her own research. She doesn't need the actual journals or papers, just the names, dates, etc. for reference. Each journal has a name, a publisher, number of times per year it is published. Each article can appear in only one journal and she will keep track of the date it was published. Each article can have one or more authors and each author can contribute to any number of articles. For each author she wants to track the first and last name and affiliation (UO, Microsoft, etc). Draw an ER diagram to model the journals, articles, and authors, including the attributes described above, and the relationships between them.