Business Rules (CDM/LDM/PDM)

A business rule can represent a government-imposed law, a customer requirement, or an internal guideline. They may start as simple observations, such as "customers call toll-free numbers to place orders", and develop into more detailed expressions during the design process such as what information a customer supplies when placing an order or how much a customer can spend based on a credit limit.

Business rules complement your diagrams with information that is not easily represented graphically, and can help guide the creation of a model. For example, the rule "an employee belongs to only one division" can help you define the link between an employee and a division. Business rules are generated as part of intermodel generation and can be further specified in the generated model.

There are three ways to use business rules in a data model:

Apply a business rule to a model object as part of its definition (see Attaching a Business Rule to a Model Object).
[PDM only] Create a server expression that can be generated to a database (see Creating and Attaching a Constraint Rule).
[PDM only] Insert a business rule expression in a trigger or stored procedure using the .CLIENTEXPRESSION or .SERVEREXPRESSION macros (see Customizing and Extending PowerDesigner > DBMS Definition Files > PDM Variables and Macros).

When creating business rules, you may find it helpful to ask the following kinds of question:

Do any mandatory regulations impact my system?
How can I clearly and concisely define the specifications for my project?
Do any constraints limit my options?
Is this rule a definition, fact, formula, or avalidation rule?

Creating a Business Rule
You can create a business rule from the Browser or Model menu, or from the Rules tab of an object property sheet.
Business Rule Properties
To view or edit a business rule's properties, double-click its Browser or list entry. The property sheet tabs and fields listed here are those available by default, before any customization of the interface by you or an administrator.
Attaching a Business Rule to a Model Object
You can attach a business rule to a model object from the object's property sheet.
Creating and Attaching a Constraint Rule
Validate and constraint business rules have their expressions generated as constaints for DBMSs where this is supported. Validate rules can be reused by multiple objects, but constraint rules can only be used once, and will be generated as a separate constraint for DBMSs that support multiple constraints.

Parent topic: Physical Diagrams