The ability to ensure you can retrieve persisted data without error is of primary importance. Without data confidence, no query answer can be guaranteed to be correct, and there is not much point in worrying about data availability or performance.
Thus far in the chapter you have seen methods to review and query your data for quality using implicit means. In this section, you will take a proactive approach to data integrity through explicit definitions.
Your first concern is to make certain that you have exactly one master copy of the data that is used throughout the enterprise. Then, to be proactive, you must explicitly define the data using entity and attribute values.
It goes without saying, but we will say it anyway: ...