1. Lecture: Business Rules
BTS330
Lecture: Business Rules

2. What is a Business Rule?
“…a statement that defines or constrains some aspect of the business.”
(Software Requirements Development, K. Wiegers, p. 154)

3. CASE STUDY RFERENCE
All information used in this presentation is derived from the following website:
EU-Rent's car rental business

4. POLICY a general statement of direction for an enterprise.
An example of a policy for EU-Rent's car rental business might be:
"We only rent cars in legal, roadworthy condition to our customers."

5. BUSINESS RULE STATEMENT
a declarative statement of structure or constraint that the business places upon itself or has placed upon it.
For example, each of the following could be a business rule statement for EU-Rent:
"Cars should be checked on return from each rental, and on transfer between branches."
"If any lights are not working, the bulbs should be replaced. If tires are worn, they should be replaced."
"Under any of the following conditions the car should be scheduled for service or repair:
accumulated mileage since the last service is greater than 5000,
the brakes are not satisfactory,
the exhaust is noisy or emitting fumes,
there is any damage to body work (apart from superficial dents and scratches), lights or glass,
there are any significant fluid leaks."

6. BUSINESS RULE
a statement that defines or constrains some aspect of the business. This must be either a term or fact (described below as a structural assertion), a constraint (described below as an action assertion), or a derivation. It is 'atomic' in that it cannot be broken down or decomposed further into more detailed business rules. If reduced any further, there would be loss of important information about the business.
For example, a business rule for EU-Rent might be:
"A car with accumulated mileage greater than 5000 since its last service must be scheduled for service."

7. Examples Each order must have a shipping charge
A library customer cannot borrow more than 10 books
If stock drops to below the minimum shelf level then the system generates a purchase order
If a customer purchases between 10 and 20 books, she/he gets a 15% discount
If payment is not received within 30 days of the invoice date then the account is delinquent

8. More Examples Each movie department must have a producer
Video System: A limit to the number of videos that can be borrow
Scheduling Youth Hockey: A limit to how late into the evening a hockey player of a certain level can play

9. More Examples
Movie Project Management: When a task is completed, the system sends an notifying all the producers.
An order of less than n items has a specific shipping charge. For each additional n items the shipping charge increases by x.
If the customer has not purchased anything for 18 months, the customer is inactive.

10. Ambler Reference