What are Business Rules?
Definition: A business rule defines or constrains some aspect of business and always resolves to either true or false. – Wikipedia
It clearly states what a business must or must not do. There is no grey area there.
They are clear-cut opaque rules with black and white answers.
They guide how a business must strictly function.
They define how you do business or you don’t do business
They are statements or conditions that state if a specific action can be performed in a given business.
Purpose: Business rules are intended to assert business structure or to control or influence the behavior of the business. Business rules describe the operations, definitions, and constraints that apply to an organization.
Business Rules give a structure to your business. It makes you sure of the business’ operations.
In the business’ context, if a question is asked, “Does the business do this activity or does it perform this operation?” you should be able to give a resounding yes or no. If that is not the case then formulate a business rule for it.
Business rules must never change. However, first, understand if a rule is at all needed.
Business Rules vs Business Requirements
Business Requirements: These may include what needs to be done to enable the business rule to be implemented. In other words, a business requirement may not be valid if it contradicts or breaks an existing business rule. (source)
Business requirements validate and enforce business rules.
E.g. 1
Business Rule: Only accept valid email addresses in the system.
Explanation: The rule clearly states that the system should always store valid email addresses.
Requirements:
- The system shall have the capability to accept email addresses
- The system shall validate that the entered email is having the correct structure (always contains @ and .)
- The system shall allow for correction of an invalid email address
E.g. 2
Business Rule: A quote must be completed prior to an invoice being generated.
Explanation: The above rule states that every invoice should always have an associated quote.
Requirements:
- The system shall have the capability to enter a quote
- The system shall automatically move the quote details to the invoice
- The system shall maintain the relationship between the invoice and quotes
- The system shall generate a report of invoices and their associated quotes
Best Practices for Business Rules
Document business rules and keep them simple.
You may have them in the same document as the requirements document or you can have them in a separate document based on the company’s policy.
Business requirements are expected to follow and respect the business rules.
The business requirements give the assurance that a particular business rule is met.
If a business rule allows for or constrains a capability then its equivalent requirements ensure the rule is enforced.
Each business rule may need multiple requirements.
A business rule should not be changed.
Business rules are part of the foundation and the architecture of a project.
In rare cases, a business rule can change but then the business should be made aware that the changes to a business rule may cause major implications in the future.
If a business suggests that a rule has the potential to change then never note it as a business rule.
Business rules should not be taken lightly.
E.g.
Business Rule: Each course must have at least one instructor.
Requirements:
- The system shall have the capability for the course coordinator to assign an instructor to a course.
- The system shall allow the course registration to open after an instructor is assigned.
Currently, there is no provision for self-paced online classes and hence the above rule works. But if the company plans to have self-paced online classes in the future then the above rule may not apply. Hence carefully evaluate if the above rule should be strictly implemented or not.
If the business plans to have self-paced online classes in the future then it would be better to not have it as a rule and instead have it as a regular requirement that states the class can have zero or one instructor. This way you can create courses without instructors and not change any business rule which could have had serious implications for the system.
The post is based on my notes and understanding from this BA tutorial