Design patterns·Modelling the domain
two of them with identical fields are still different things, because the thing that makes them the same is the id.
Entity
Also calledentity object, reference object
An object defined by a continuous identity rather than by its attributes: a customer who changes name and address is the same customer. Identity is what forces an entity to have a lifecycle, to be tracked, and to be compared by id rather than by value. Getting the entity-or-value question right for each concept is the single highest-leverage modelling decision in this cluster.