Business Logic

In short: The business logic contains the domain rules of an application.

In more detail: It determines what is allowed from a business point of view and how things are calculated: pricing, discounts, checks, workflows.

In Depth

Distinction

It belongs neither in the user interface (presentation tier) nor in data access (data tier), but in the middle layer (logic tier).

Example

“Shipping is free from 50 euros of goods value” is business logic. It is implemented and tested centrally. See SRP.

See also: Logic Tier, Presentation Tier, Data Tier, SRP