CS145 - Introduction to Databases
Spring 2000, Prof. Widom

Written Assignment #1
Due Wednesday April 12

Turn-in procedure and late policy reminder

The assignment

Problem 1

In the E/R model, consider a relationship set R between two entity sets E1 and E2. Does it ever make sense for the same pair of entities e1 (from E1) and e2 (from E2) to participate in the relationship set more than once? That is, might we ever want to have two (or more) instances of (e1, e2) in R? If not, explain why not. If so, give a real-world example: give details of two entity sets and a relationship set that model a real-world domain where we might have a pair of entities related more than once.

Problem 2

Hints: There is some interplay between Problem 1 and at least one part of this problem, and not every part of this problem necessarily has a single correct answer.

Problem 3

Find a site on the Web for which you're quite sure there is a database management system operating behind the scenes. If the site you select has a wide variety of data and a very powerful interface, try to isolate a smaller portion of the site (or choose a simpler site).

Problem 4

You are to design a database for an insurance company. The data will include information about customers (name, address, and phone number), information about insured cars (make, model, year, vehicle-ID#, license#, and insurance rate), information about insured homes (address, insured value, and insurance rate), and information about claims made on insured cars and homes (date of claim, date of settlement, and amount of settlement). You may assume that all insured cars and homes are owned by a single customer, but you should allow a customer to own several cars and homes. Please state any additional assumptions you make about the real world in your design. Note: There is no single right answer to this question by any means, although some answers may be better than others.

Problem 5

Consider the four relations on pages 188-189 of the Ullman/Widom textbook. These relations contain a database for describing PC's, laptops, and printers.