Business Rules vs. Business Requirements
I am asked this all the time. What is the difference between a business rule and a business requirement? It is simple, really. Business rules are lists of statements that tell you whether you may or may not do something, or give you the criteria and conditions for making a decision. One factor of a business requirement is what you need to do to enable the implementation of and compliance with a business rule.
Believe it or not, my daughter will be turning thirteen this summer. She is definitely a twelve year old going on twenty-one. One Saturday morning during breakfast, we got into a conversation about what some of her rules will be when she is old enough to go out on her own (I say around sixteen or seventeen... her dad would say twenty-five).
Here are my rules to my daughter:
- Must not stay out past 10:30 pm. (Of course there were grumbles.)
- Must not let a new driver (this includes all her friends) drive you home without
my permission. (I got one of those looks and an "Oh! Mooommmm!")
- I must know where you are at all times. (I got an "Oh, boy!"
and a big sigh!)
- Must not go in a car with someone I don't know. (I got a big fat "WHAT!
You might not know all my friends when I am sixteen, you know.")
- Must not go anywhere with a stranger. (I got an "I am not stupid, you know!")
So I said those are the rules -- take it or be prepared to stay home through your teenage years.
She thought about it for a little while and said ok. However, she said she has one requirement. She needs a car!
There you go — she requires a car in order to comply with the rules.
Here are some questions for the readers:
- Do the rules exist even when you can't implement the requirement? Absolutely.
- Will implementing the requirement mean all the rules will be complied with?
Not for sure.
- Will implementing the requirement enable easier compliance with the rules?
- Is this the ONLY feasible requirement to enable compliance with this set of rules? No.
How does this relate to your projects?
Consider the following examples:
Example 1: License Inspection Project
A Driver of a Vehicle must have a valid Driver's License.
A Driver's License must be considered valid if all of the following are true:
- The Driver's License belongs to the Driver.
- The Expiry Date of the Driver's License is later than the Inspection Date.
- The physical proof is produced within 24 hours of the Inspection Date.
Possible business requirements to enforce these rules:
- Police officer to inspect driver's license.
- Scanner to read driver's license for validity.
- Card reader for driver to insert driver's license when driving through a checkpoint.
Any one of these requirements can enforce the above 2 rules with different degrees of efficiency and effectiveness. Which business requirements are appropriate largely depends on the corporation's business strategies, business risk tolerance, and budget.
The important point to remember is that the business rules are what we need to guide behavior. However you choose to implement or enforce those rules is a different matter. Do not confuse the two.
Example 2: Order Entry System
A Customer must have an Email Address.
Capability to enter email address for a customer.
This can easily be implemented by providing a GUI to enter an email address.
Now consider a simple change to the business rule:
Revised Rule: A Customer must have a valid Email Address.
A second rule is required to define 'valid email address'.
Rule 2: An Email Address must be considered Valid if an email sent to Email Address does not return 'undeliverable' within 60 minutes.
Additional Business Requirement to support revised rule:
Capability to immediately send email to customer after email address is received.
Notice how the change of one word in a business rule can mean different or additional requirements. Keep in mind one affects the other.
The question I want to leave you with now is: What do you need to manage? The rules or the requirements?
Plainly speaking, here are some of the main things you need to remember:
- Business rules are lists of statements that tell you whether you may or may not
do something or that give you the criteria and conditions for making a decision.
- Business requirements are what you need to do to enable the implementation of
and compliance with business rules.
- There can be many different alternative business requirements to implement/enforce
a set of business rules.
- Business rules are what they are. They shouldn't change to fit the business
- A change in a rule can mean different or additional requirements.
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