Review your answers, feedback, and question scores below. An asterisk (*) indicates a correct answer.
Modeling Change: Price
(Answer all questions in this section)
1. Why would you want to model a time component when designing a system that lets people buy bars of gold? Mark for Review
(1) Points
The price of gold fluctuates and for determining price, you need to know the time of purchase (*)
To allow the sales people to determine where the gold is coming from
You would not want to model this, it is not important
The Government of your country might want to be notified of this transaction.
2. Which of the following is a logical constraint that could result from considering how time impacts an example of data storage? Mark for Review
(1) Points
End Date must be before the Start Date.
ASSIGNMENT periods can overlap causing the database to crash.
An ASSIGNMENT may only refer to a COUNTRY that is valid at the Start Date of the ASSIGNMENT. (*)
Dates can be valued only with Time.
3. What is the function of logging or journaling in conceptual data models? Mark for Review
(1) Points
Allows you to track the history of attribute values, relationships and/or entire entities (*)
Gives a timestamp to all entities
Represents entities as time in the data model
Creates a fixed time for all events in a data model
4. You are doing a data model for a computer sales company, where the price goes down on a regular basis. If you want to allow them to modify the price and keep track of the changes, what is the best way to model this? Mark for Review
(1) Points
A. Create a product entity and a related price entity with start and end dates, and then let the users enter the new price whenever required.
B. Create a new item and a new price every day.
C. Use a price entity with a start and end date
D. Allow them to delete the item and enter a new one.
E. Both A and C (*)
