What is Business Logic?

Business logic is the set of rules that governs how a user interface interacts with the data within its jurisdiction. It is the collection of “if, then” scenarios that dictate how a system will perform its required functionality, and it serves as the underpinning of any software.

Business Logic vs. Application Logic

Business logic determines how data will be stored, used, manipulated, and presented to the user. It comprises the governing body of laws that inform an organization’s services “what to do.”

By contrast, an organization’s application logic instructs its software “how to do” what the business logic tells it to do. While business logic encompasses a set of rules defining the purpose of the service and what it is designed to do, application logic provides the technical aspects and laws governing how those objectives are achieved.

Application logic includes essential operations including:

• Routing links to certain pages within a website.
• Authenticating access to services. This includes people and processes.
• Managing how data is protected, stored, displayed, and retrieved within an application.

Examples of Business Logic

Any time a software system automatically carries out an operation, it is based on the business logic within its programming. Real-world examples of business logic include:

• A CRM is programmed to automatically update its customer contact backups when a new customer is added.
• An online retail site automatically calculates sales tax and discounts.
• Digital banking services automatically calculate loan pre-approvals, interest, and applicable fees.

What is the Business Logic Layer?

It is a best practice in many applications to separate the business logic from the database and the user interface. This is to allow developers the freedom to alter the business logic without interfering with the data in the database or the way in which users see that data displayed. When the needs of the business change, the business logic must change with it; such a separation allows organizations to stay both resilient and safe.

All the rules, workflows, and constructs that comprise an organization’s business logic are contained in the Business Logic Layer (BLL), also referred to as the Domain Logic Layer (DLL). The business logic layer resides between the database and user interface, as follows:

• Presentation layer (user interface.)
• Business logic layer.
• Data access layer (database.)

The business logic layer retrieves data from the database, manipulates it according to its predefined rules, and then presents it via the user interface.

The 3 Fundamentals of Business Logic

Regardless of application, three fundamental principles are common components of business logic in nearly any scenario:

1. Data consistency: Ensures data consistency within services, such as updating price lists and making sure products are uniformly displayed.
2. Participant control: Enforces who can access and alter data within the service or application.
3. Modification checks: Audits changes to data to ensure they are consistent with internal rules. For example, modification checks prevent employees from entering false values for item numbers or tampering with data in a way that would lead to inaccurate reporting.

A company’s proprietary business logic can set it apart from competitors and define the services that make it unique. It is the key to what a company’s applications or services do.

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