6.1

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. Each insurance policy covers one or more cars and has one or more premium payments associated with it. Each payment is for a particular period of time, and has an associated due date, and the date when the payment was received.

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One possible ER diagram is shown in Figure 6.101. Payments are modeled as weak entities since they are related to a specific policy. Note that the participation of accident in the relationship participated is not total, since it is possible that there is an accident report where the participating car is unknown.

Note that the double-line connecting the entity set car to the relationship participated should be a single-line, since we could have cars that have not participated in any accident until now. That is, the participation of the entity car in the relationship participated is not total, thus it is partial.

Also note that, given a premium_payment we can not identify for which car that premium_payment was made for. So there is some bug that needs to get fixed in the E-R diagram if we want to determine the car given a premium_payment info.