Fordham, New York City's Jesuit University
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FORDHAM UNIVERSITY, Fordham College Lincoln Center
CSEU 3500 -- Data Base Systems
Dept. of Computer & Info. Sciences, Spring, 2004

Homework for Chapter 2
Due date: Wednesday, February 18

[10 pts.] Explain the distinctions among the terms primary key, candidate key, and superkey.
[15 pts.] Construct an E-R diagram for a car insurance company whose customers own one or more cars each. Each car has associated with it zero to any number of recorded accidents. [Document i.e. make explicit, all the assumptions you make about mapping constraints.]

[In your design, include all the attributes explicitly mentioned, as well as a few reasonable additional ones that would be needed in a real design. (In particular, each strong entity set should have a key and each weak set a discriminator.) Your design does not need to be as complete as a real one would be. You may make any reasonable assumptions about mapping constraints. In other words, there is no single ``right answer'' to this question.]

[15 pts.] Construct an E-R diagram for a hospital with a set of patients and a set of medical doctors. Associate with each patient a log of the various tests and examinations conducted. [Include a reasonable number of attributes for each entity. Document all the assumptions you make about mapping constraints.]

[20 pts.] A university registrar's office maintains data about the following entities: (a) courses, including number, title, credits, syllabus, and prerequisites; (b) course offerings, including course number, year, semester, section number, instructor(s), timings, and classroom; (c) students, including student-id, name, and program; and (d) instructors, including identification number, name, department, and title. Further, the enrollment of students in courses and grades awarded to students in each course they are enrolled for must be appropriately modeled.

Construct an E-R diagram for the registrar's office. Document all the assumptions you make about the mapping constraints.

[Your design should include only the attributes mentioned, unless you find that an entity set that should be strong requires another attribute in order to have a key. You may split some of the above-listed entities into separate entities if you find it appropriate or convenient to do so. You may make any reasonable assumptions about mapping constraints.]

[20 pts.] Consider a university database for the scheduling of classrooms for final exams. This database could be modeled as the single entity set exam, with attributes course-name, section-number, room-number, and time. Alternatively, one or more additional entity sets could be defined, along with relationship sets to replace some attributes of the exam entity set, as:
Show an E-R diagram illustrating the original design, and another diagram illustrating the use of all three additional entity sets listed.

Explain what application characteristics would influence a decision to include or not to include each of the additional entity sets.

Robert Moniot 2004-02-04