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Section8 Homework

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Section 8
Vocabulary - Directions: Identify the vocabulary word for each definition below.
1. Time-related constraint
A constraint or data restriction that results from
the time dimension.
2. Conditional nontransferability
Refers to a relationship that may or may not be
transferable, depending on time.
3. Nontransferability
Property of a relationship where an instance of
A is related to an instance of B, and the
association cannot be moved to another instance
of B
1. Speeding Tickets
Each police officer may issue speeding tickets to motorists in an assigned area. Originally, the
attribute date was modeled as part of the SPEEDING TICKET entity. However, the city police
department wants to see if there is a relationship between weather and the frequency of
speeding tickets -- do people drive faster on nice sunny days? Are there more tickets in hot
weather or cool weather?
Does the ERD have to be modified for this new requirement?
YES: a new entity should be added to store each days weather conditions.
Traffic Officer
#ID
*precinct
*

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2. Examine the ERD that represents classroom assignments for different exams.
a. Why is start time part of the UID of ASSIGNMENT?
Start time should be part of the UID to identity each assignment start time. One exam can have many
assignments placed in a given classroom. The ASSIGNMENT entity therefore requires a start time to
identify each assignment.
b. Name at least three time-related constraints.
An exam can only be unassigned before start time but not in between the start time and end time. This is
known as conditional non-tranferability.
Start time and end time are only time e.g. 11:30 hence are not in the DateTime format. Time and date have
been separated since the exams may not be finished in the same day.
Each exam must have at least one day and start time. In this same day the exam must be assigned a class.

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Section 8 Vocabulary - Directions: Identify the vocabulary word for each definition below. 1. Time-related constraint 2. Conditional nontransferability 3. Nontransferability A constraint or data restriction that results from the time dimension. Refers to a relationship that may or may not be transferable, depending on time. Property of a relationship where an instance of A is related to an instance of B, and the association cannot be moved to another instance of B 1. Speeding Tickets Each police officer may issue speeding tickets to motorists in an assigned area. Originally, the attribute date was modeled as part of the SPEEDING TICKET entity. However, the city police department wants to see if there is a relationship between weather and the frequency of speeding tickets -- do people drive faster on nice sunny days? Are there more tickets in hot weather or cool weather? Does the ERD ha ...
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