Entities and value objects

DDD entities represent domain objects that have a well-defined identity, as well as all the operations that are defined on them. They don’t differ too much from the entities of other, more classical approaches. Also, DDD entities are the starting point of the storage layer design.

The main difference is that DDD stresses their object-oriented nature, while other approaches use them mainly as records whose properties can be written/updated without too many constraints. DDD, on the other hand, forces strong SOLID principles on them to ensure that only certain information is encapsulated inside of them and that only certain information is accessible from outside of them, to stipulate which operations are allowed on them, and to set which business-level validation criteria apply to them.

In other words, DDD entities are richer than the entities of record-based approaches.

In other approaches, operations that manipulate entities are defined...