Chapter 4. Data Integrity
Creating a model of the entities in the problem space and the relationships between them is only part of the data modeling process. You must also capture the rules that the database system will use to ensure that the actual physical data stored in it is, if not correct, at least plausible. In other words, you must model the data integrity.
It’s important to understand that the chances of being able to guarantee the literal correctness of the data are diminishingly small. Take, for example, an order record showing that Mary Smith purchased 17 hacksaws on July 15, 1999. The database system can ensure that Mary Smith is a customer known to the system, that the company does indeed sell hacksaws, and that it was taking orders ...
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