DMLab3 Answer the following questions from chapter 5. The first four, 5.10, 5.11, 5.12, 5.28 are worth 10 points apiece. 5.59 is worth 60 points.
5.10 Define relationship. Give an example of a relationship (other than one presented in this chapter). Name your relationship.
5.11 Explain the difference between a relationship class and a relationship instance.
5.12 What is the degree of relationship? Give an example of a relationship of degree three (other than one presented in this chapter).
5.28 What distinguishes a weak entity from a strong entity that has a required relationship to another entity?
Problem 5.59 asks you to model a database recording WSP traffic citations. Use an ER diagram to do parts A and B. In part B post to the week 5 discussion group for the “…cardinalities…that need to be checked out with the system users”. I will act the role of the system user. Note that I’ve added additional parts to 5.59. The intent is for you to model this database for DMLab3 and then to build and populate it for DMLab4.
Note about ER diagramming software. All of you have access to Visio through DreamSpark. However, Visio is not the best software to use as it can’t model a many-to-many relationship. Instead it must model a many-to-many relationship as two 1-many relationships to a link (or intersection) table. See chapter 6 for more information about intersection tables.
I use yEd, http://www.yworks.com/en/products_yed_about.html, which does a pretty good job, but takes some getting use to; not because it’s hard, but because it’s different. It’ll draw many-to-many relationships by drawing a 1-to-many relationship from the first to the second entity and then drawing a 1-to-many relationship from the second to the first entity, as shown below:
5.59 Consider the traffic citation shown in Figure