How to Build a Business Rules Engine

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Thus far the rule types that have been discussed have not used subtypes to restrict

update operations. 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.

In the design approach followed here a subtype is identified by a single indica-

tor column in the table, or a single value of a reference data code value in a column

of the table. 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. Alternatively ...