In computer software, business logic or domain logic is the part of the program that encodes the real-world business rules that determine how data can be created, stored, and changed. It is contrasted with the remainder of the software that might be concerned with lower-level details of managing a database or displaying the user interface, system infrastructure, or generally connecting various parts of the program.

Business logic:

Business rules:

Business logic comprises:

Business logic should be distinguished from business rules. Business logic is the portion of an enterprise system which determines how data is transformed or calculated, and how it is routed to people or software (workflow). Business rules are formal expressions of business policy. Anything that is a process or procedure is business logic, and anything that is neither a process nor a procedure is a business rule. Welcoming a new visitor is a process (workflow) consisting of steps to be taken, whereas saying every new visitor must be welcomed is a business rule. Further, business logic is procedural whereas business rules are declarative.

For example, an e-commerce website might allow visitors to add items to a shopping cart, specify a shipping address, and supply payment information. The business logic of the website might include a workflow such as:

There will also be business rules of the website:

The web site software also contains other code which is not considered part of business logic nor business rules: