We have looked at a few instances of business rules previously. Business rules in general are very important in the database design process as they’ll play a role in understanding the relationships in the database, data types, data sizes as well as the constraints within the database and externally. Not all business rules will directly apply to the database design rules but it is still a good idea to be aware of what they may be as they could affect the database design.
The database to an organization is only as useful if it reflects its business rules. The business rule itself is a brief, precise description of the procedure or policy in the organization. These business rules are generally defined based on the organization’s business operations. These business rules should be defined in writing and if the organization makes any changes to the business process, this must be reflected as part of the process as well.
You have already run into quite a number of the business rules already that have been covered especially around cardinality. With any business rule, they can be used to define the entities, attributes, relationships, and constraints within the database. It is very important that the business rules are easy to understand and consistent across all users of the business. It is important that the business rules are not just written from a specific type of user but rather a general view from all users. This way, the business rules can be used as a communication tool between all of the users and the database designer. Having a standardized view of the organization’s view data will help create a level of consistency that will be accurate.
If we only get business rules from a single source, we may have situations where the business rules do not reflect the view of all of those in the organization. A great starting point in finding the business rules is to look at some of the written documentation of the company’s procedures, standards, and manual but some of those may not be consistently updated. Another source is to ask management as well as the end-users. The end-users in particular are the ones that interact with the business processes on a daily basis and have a strong understanding of how things work.
However, there may be certain business processes that may differ in the approach. For example, an employee may consider the fact that they could update any customer record. However, management may define it such that only a customer’s support representative or their manager could change the customer’s data. Although it is a small distinction, that will change the business rule associated with this criterion. Not all business processes may be defined in the database directly as in this case, but it should be represented by the application software that would make use of the databases.