Spring 2004
V. Matos / (Take home) Exam-1.
Due date: Th. Feb. 12.
u Jefferson Dance Club Database. (p.113 – 3.43)
3.43 The Jefferson Dance Club teaches social dancing and offers both private and group lessons. Jefferson charges $45 per hour per student (or couple) for a private lesson and charges $6 per hour per student for a group lesson. Private lessons are offered six days per week (from noon until 10 p.m.). Group lessons are offered in the evenings.
Jefferson employs two types of instructors: full-time salaried instructors and part-time instructors. The full-time instructors are paid a fixed amount per week, and the part-time instructors are paid either a set amount for an evening or a set amount for teaching a particular class.
In addition to the lessons, Jefferson sponsors two weekly social dances featuring recorded music. The admission charge is $5 per person. The Friday night dance is the more popular and averages around 80 people; the Sunday night dance attracts about 30 attendees. The purpose of the dances is to give the students a place in which to practice their skills. No food or drinks are served.
Jefferson wants to develop an information system to keep track of students and the classes they have taken. Jefferson’s managers also want to know how many and which types of lessons each teacher has taught and to compute the average revenue generated per lesson for each of their instructors.
Suppose Jefferson has hired you to construct a database for them. To do this, you decide to create a data model. You know you will need to interview users and gather forms, reports, and other requirements. Before you do this, however, you decide to construct a trial data model. You are hoping that this model will help you determine specific questions that you will need to ask Jefferson personnel.
A. To construct such a trial model, read through the preceding description and pick out all of the important nouns. From these nouns, construct a list of potential entities.
B. Review the list you made in A and eliminate any synonyms. Also, identify entities that are subtypes or category entities. Name a likely identifier for each entity. Eliminate any hard-to-justify entities.
C. This description does not provide sufficient data for you to specify attributes of the entities you have identified. Therefore, create a CROWFEET (or IDEF1X ) diagram that shows only entities and relationships. Name each relationship and specify its cardinalities. Justify the cardinality decisions you make
D. Do you think the process of creating a trial data model before interviewing users is a good idea? What are the advantages? What are the disadvantages?