In Business Intelligence we often have complex logic for categorizing facts. We also have even more compelling reasons to use decision tables for these calculations.
They make the logic behind the calculation transparent to the entire organisation.
Because the people who depend on the information can understand the decision table, ownership of the transformation rules passes from the programmers to the business. The business modify it as and when they please instead of waiting.
And, because the logic is easier to see, the effort involved in the initial creation, testing, and on-going maintenance is reduced regardless of who does the work.
Read the rest on the Optimal BI blog.