Entities

An Entity is an object that embodies a small set of Critical Business Rules operating on Critical Business Data. The Entity object either contains the Critical Business Data or has very easy access to that data. The interface of the Entity consists of the functions that implement the critical business rules that operate on that data.

Example loan entity as a class in UML.

When we create this kind of class, we are gatering together the software that iomplements a concept that is critical to the business, and separating it from every other concern in the automated system we are building. This class stands alone as a representative of the business. It is unsullied with concernes about databases, user interfaces, or third-party frameworks.

The Entity is pure business and nothing else.