19 - Implementing Rule Types Using Relationships and Subtypes

Abstract

Being able to work with relationships is a vital part of any rules engine design, and it is seen as something that arises in a number of different contexts. The chapter introduces various subtypes and several additional concepts that must be understood when subtypes are used. Subtypes can also figure prominently in the rules that do not involve relationships. So subtypes are groups of related records that exist within a database table. A subtype nearly always has special business rules that operate on the records that belong to it but not on the other records in the table. This is why subtypes are so important in any consideration of business rules. There may be complex conditions, expressed in business rules, which lead to the population of the indicator column or the reference data code value that identifies the subtype. If this is not done, the rules engine designer faces the problem of trying to incorporate the logic to identify the subtype within the special rules that operate only on the subtype.