THE BUSINESS RULES PARADIGM The concept of business rules has been used in

The business rules paradigm the concept of business

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THE BUSINESS RULES PARADIGM The concept of business rules has been used in infor- mation systems for some time. There are many software products that help organiza- tions manage their business rules (for example, JRules from ILOG, an IBM company). In the database world, it has been more common to use the related term integrity con- straint when referring to such rules. The intent of this term is somewhat more limited in scope, usually referring to maintaining valid data values and relationships in the database. A business rules approach is based on the following premises: • Business rules are a core concept in an enterprise because they are an expression of business policy and guide individual and aggregate behavior. Well-structured business rules can be stated in natural language for end users and in a data model for systems developers.
64 Part II Database Analysis • Business rules can be expressed in terms that are familiar to end users. Thus, users can define and then maintain their own rules. • Business rules are highly maintainable. They are stored in a central repository, and each rule is expressed only once, then shared throughout the organization. Each rule is discovered and documented only once, to be applied in all systems devel- opment projects. • Enforcement of business rules can be automated through the use of software that can interpret the rules and enforce them using the integrity mechanisms of the database management system (Moriarty, 2000). Although much progress has been made, the industry has not realized all of these objectives to date (Owen, 2004). Possibly the premise with greatest potential benefit is “Business rules are highly maintainable.” The ability to specify and main- tain the requirements for information systems as a set of rules has considerable power when coupled with an ability to generate automatically information systems from a repository of rules. Automatic generation and maintenance of systems will not only simplify the systems development process but also will improve the quality of systems. Scope of Business Rules In this chapter and the next, we are concerned with business rules that impact only an organization’s databases. Most organizations have a host of rules and/or policies that fall outside this definition. For example, the rule “Friday is business casual dress day” may be an important policy statement, but it has no immediate impact on databases. In contrast, the rule “A student may register for a section of a course only if he or she has successfully completed the prerequisites for that course” is within our scope because it constrains the transactions that may be processed against the database. In particular, it causes any transaction to be rejected that attempts to register a student who does not have the necessary prerequisites. Some business rules cannot be represented in com- mon data modeling notation; those rules that cannot be represented in a variation of an entity-relationship diagram are stated in natural language, and some can be repre- sented in the relational data model, which we describe in Chapter 4.

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