Chapter 4. The Business Layer

Any fool can write code that a computer can understand. Good programmers write code that humans can understand.

Martin Fowler

Any software of any reasonable level of complexity is organized in layers. Each layer represents a logical section of the system. In particular, the modules in the business layer include all the functional algorithms and calculations that make the system work and interact with other layers, including the data access layer (DAL) and presentation layer.

The business layer is the nerve center of any layered system and contains most of its core logic. For this reason, it is often referred to as the business logic layer (BLL). In the rest of this chapter, we’ll primarily use the BLL acronym to indicate ...

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