Implementing Domain-Driven Design

Why We Use Entities

We design a domain concept as an Entity when we care about its individuality, when distinguishing it from all other objects in a system is a mandatory constraint. An Entity is a unique thing and is capable of being changed continuously over a long period of time. Changes may be so extensive that the object might seem much different from what it once was. Yet, it is the same object by identity.

As the object changes, we may be interested in tracking when, how, and by whom changes were made. Or we might be satisfied that its current form implies enough about its previous state transitions that explicit change tracking is unnecessary. Even if we don’t decide to track every detail of its change history, we could still reason ...