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Functional Categories of Business Rules

Chapter 10. Functional Categories of Rules: The BRS Rule Classification Scheme
The BRS Rule Classification Scheme reflects how rules react to events. A given rule can react in one of only three possible ways to an event—hence there are three fundamental categories of rules in the scheme.
These three categories, which are defined in Table 10-1, arerejectors, producers, and projectors. Because these three categories are intrinsic, definitive, and mutually exclusive, they provide a sound foundation for the comprehensive set of rule sentence templates in RuleSpeak. They also have well-defined subcategories, as the table also indicates. These subcategories provide an even richer basis for organizing the templates—as well as for gaining a betterunderstanding of your company's rules.
Table 10-1. The BRS Rule Classification Scheme |
Functional Category/ Subcategory | Common Name | Definition |
1.0. Rejector | Constraint[a] | Any rule that tends to disallow (that is, reject) an event if a violation of the rule would result. Rejectors shield the business from incorrect data (or incorrect state)—that is, from information that violatesbusiness rules.For example, a rejector might be specified to prevent a customer from placing an order on credit if the customer has a poor payment history. |
2.0. Producer | — | Any rule that neither rejects nor projects events but simply computes or derives a value based on some mathematical function(s). |
2.1. Computation rule | — | Any producer-type rule that computes a value followingstandard arithmetic operations (for example, sum, multiply, average, and so on) specified explicitly. A computation rule provides a precise formula for how a computed term is to be calculated.For example, a computation rule might be given to compute a customers' annual order volume. |
2.2. Derivation rule | — | Any producer-type rule that derives a truth value (that is, true or false) based on logicaloperations (for example, AND, OR, NOT, EQUAL TO, and so on) specified explicitly. A derivation rule provides a precise definition for a derived term—that is, a truth-valued term whose value (true or false) is always established by the specified logical operations.For example, a derivation rule might be given to indicate whether a project is at risk depending on whether the project is over budgetor understaffed. |
3.0. Projector | Stimulus/response rule | Any rule that tends to take some action (other than rejection) when a relevant event occurs. A projector never rejects events (as rejectors do); rather, it projects them—that is, causes some new event(s) to occur as a result. Projectors generally prescribe automatic system behavior, providing a productivity boost for workers.Forexample, a projector might be specified to reorder stock automatically if the quantity on hand drops below a certain point. |
3.1. Enabler | Toggle | A projector that toggles something on or off. |
3.1.1. Inference rule | — | An enabler that infers something to be true under appropriate circumstances.For example, an inference rule might be given to indicate that a person must be considered a woman ifcriteria for that person's age and gender are satisfied. |
3.1.2. Rule toggle | Exception-type rule | An enabler that turns another rule on or off under appropriate circumstances—that is, makes it capable or incapable of firing.For example, a rule toggle might be given to indicate that some normal operating rule is to be suspended under emergency circumstances. |
3.1.3. Process toggle | — |An enabler that turns an operation, process, or procedure on or off under appropriate circumstances—that is, makes it capable or incapable of executing.For example, a process toggle might be given to indicate that a sensitive process cannot be executed while a security breach is suspected. |
3.1.4. Data toggle | — | An enabler that creates or deletes instances of actual data under appropriate...