Consider the Is_married_to unary relationship in Figure 8.14c.

a. Assume that we want to know the date on which a marriage occurred. Augment this E-R diagram to include a Date_married attribute.

b. Because persons sometimes remarry after the death of a spouse or a divorce, redraw this E-R diagram to show the whole history of marriages (not just the current marriage) for persons. Show the Date_married attribute on this diagram.

c. In your answer to Problem and Exercise 8.63b, is it possible to represent a situation in which the same two people marry each other a multiple number of times? Explain.

Figure 8.14

Transcribed Image Text:

(a) Mark Visit 1 Has recorded PATIENT PATIENT HISTORY Visit 1 Visit 2 Sarah Elsie -Visit 1 (b) Rose BPR Is assigned_to ΕMPLOYEΕ PROJECT Pete TQM Debbie 00 Tom CR Heidi (c) Shirley Is married_to Mack Dawn PERSON Kathy Ellis Fred