The Data Model Resource Book, Volume 3: Universal Patterns for Data Modeling

Silverston c08.tex V2 - 11/21/2008 3:12am Page 414

414 Chapter 8 ■ Business Rules: How Things Should Work

Another clue that you are modeling a rule is when you notice conditional

statements, such as ‘if, then’ statements or ‘while’ statements. For example,

if the geographic boundary of the ship-to address is in New York, and if the

quantity is greater than 100 items being ordered, and if the type of customer is

a governmental customer, then the price is $100 for this product. Or another

example, if a customer files a complaint, and if this customer is a gold loyalty

member, and if the customer has ordered more than $10,000 from you this

year, then you have a vice president call that customer.

The beauty of this pattern is that when you recognize that you are dealing

with data requirements involving business rules, you can choose to model this

and other types of business rules consistently with one of the business rules

patterns that we will share in this chapter. We have been in many situations

where we have modeled something and then realized later that this was in fact

a ‘rule’ data modeling structure. By identifying types of conditional statements

(such as ‘if, then,’ ‘while,’ or ‘in case’ statem ents) or data requirements that

are factors and/or outcomes, you can recognize rules up front. Then, using

the rules pattern, you can create more consistent data models by combining

various rules in