You'll define and establish business rules for the database during this stage of the design process. Remember that you must base these rules on the manner in which your organization perceives and uses its data, which (as you well know) will depend on the way the organization functions or conducts its business. The best approach to this task is to define and establish the field specific business rules first, followed by the relationship specific business rules. This approach helps you to remain focused on the type of rule you're defining. It also keeps you from jumping back and forth between different types of business rules, which can often lead to confusion and some amount of frustration.