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Chapter 4 How to Keep the Facts Sound Using Constraints

One aspect of data quality (an important issue nowadays; see Appendix B, [21]) is to keep the Facts that are stored in a database sound. Data pollution (Facts that are wrong or missing) is a constant threat. Although it is impossible to guarantee that the Facts stored are 100% correct (e.g., someone deliberately enters an overoptimistic body weight figure), many measures can be taken to prevent data pollution.

Most of these measures follow from Business Rules: domain requirements that the Facts should satisfy at all times like “A show belongs to one or more genres.” or “The ...

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