What is the difference between an MVC Model object, a domain object and a DTO

Question

What is the difference between a MVC Model object, a domain object and a DTO?

My understanding is:

MVC Model object:

Models the data to be displayed by a corresponding view. It may not map directly to a domain object, i.e. may include data from one or more domain objects.

1. Client side
2. May contain business logic. Eg. validations, calculated properties, etc
3. No persistence related methods

Domain object:

An object that models real-world object in the problem domain like Reservation, Customer, Order, etc. Used to persist data.

1. Server side
2. No business logic

DTO (Data Transfer Object):

An object used to transfer data between layers when the layers are in separate processes, e.g. from a DB to a client app. Allows a single transaction across the wire rather than multiple calls when fetching data corresponding to multiple domain objects. A DTO contains just data and accessor methods and there is no logic present. The data is for a particular DB transaction, so it may or may not directly map to a domain object as it may include data from one or more domain objects.

1. Used on both server and client sides as it is passed between layers
2. No business logic
3. No persistence related methods

So, the questions:

1. Is above understanding correct? Am I missing some key points?

2. Are there any reasons not to use Domain objects as the MVC Model assuming that the Model objects do not require extra business logic?

3. Are there any reasons not to use DTOs as the MVC Model assuming that the Model objects do not require extra business logic?

Answer 1

Domain and model objects are essentially the same, and may contain business logic. Depending on implementation, domain and DTO objects may be equivalent if you remove business logic from the model into a service class.

Often a key variant of the DTO is the View Model, which is used purely to transfer data between the domain model and the view, although often a View Model may contain logic, although this should be purely UI logic.