Types of Business Rules

Several sources suggest these types:

Recent writings by Ross and von Halle, as well as Object Role Modeling, establish these four categories of rules.

Since there is no formal science to business rules, these types are useful only for classification. Even those tools which support them (e.g., PowerDesigner) make little or no attempt to operate differently on the different types.

A fact type rule can express a complex relationship between what might become attributes and/or entities in an entity-relationship diagram. For example:

An employee (entity) may have an assigned parking space (entity) or monthly parking allowance amount (attribute within employee) but not both.

While this statement is a rather simple valid business fact, it cannot be modeled on an entity-relationship diagram. Such rules are sometimes captured as text as pseudo-code for procedural solutions.