After fully data profiling column properties and data structure, it is time to deal with data rules. Technically, all testing discussed in the last two chapters involves rules in that they define conditions the data must follow to be considered accurate. However, it is easier to understand and profile column and structure rules if they are cast in traditional database architecture terminology. At this point, however, the remaining rules to consider are general enough in nature that they require an expression language all to themselves.
Data rules are specific statements that define conditions that should be true all of the time. A data rule can involve a single column, multiple columns in the same table, or columns that cross over multiple tables. However, they always involve relationships between multiple tables. Rules can also be restricted to the data of a single business object or involve data that encompasses sets of business objects.
This chapter attempts to simplify the analysis process by first considering only data rules that fall within the analysis of a single business object. Dealing with sets of business objects is the topic of the next chapter.
The prior chapters have used data rule expressions to demonstrate many points. You should be fairly familiar with the syntax and intent of these rules by now. This chapter may repeat some of the information already covered. However, it is necessary to provide a thorough coverage of the material in one place to ensure complete treatment of this important data profiling step.