Assume you work at the television station and are asked to evaluate the data model in Figure CE7-12.

Suppose that you want to differentiate between prospects who have worked in the past and those who have never worked, but who are prospects for future work. Say that one of the data modelers tells you, “No problem. We’ll know that because any Prospect entity that has no relationship to a Work entity is a prospect who has never worked.” Restate the data modeler’s response in your own words.

Does this seem like a satisfactory solution? What if you want to keep Prospect data that pertains only to prospects who have worked? (No such attributes are shown in Prospect in Figure CE7-12, but say there is an attribute such as YearFirstVolunteered or some other attribute that pertains to prospects who have worked in the past.) Show an alternative E-R diagram that would differentiate between prospects who have worked in the past and those who have not. Compare and contrast your alternative to the one shown in Figure CE7-12.