value-objects

By looking to the example of a Domain Object into Zend Quickstart tutorial, and other examples considering a DAO/VO patterns, they both seem to be very similar. Can we deduce that to say "Value Object" is the same as to say "Domain Object" ? If not, can you please clarify the differences between those? What is the function of one, and what if the function of another ? I'm asking this because, both are composed by getters and setters and nothing more then that. It seems that, they do the same function... Update: So, Zend Framework Quick Tutorial documentation called this, a domain object: //

Entities and value objects are both domain objects. What's the use of knowing the distinction between the two in DDD? Eg does thinking about domain objects as being either an entity or value object foster a cleaner domain model? Yes, it is very helpful to be able to tell the difference, particularly when you are designing and implementing your types. One of the main differences is when it comes to dealing with equality, since Entities should have quite different behavior than Value Objects. Knowing whether your object is an Entity or a Value Object tells you how you should implement equality

I have gotten so far that I understand entity objects have an ID while value object have not, but in the most common example you have the person entity that have a address value object attached to it. What is the big advantage of creating a separate address object instead of just keeping the address properties within the Person Entity? In addition to the things already mentioned, Greg Young makes a big deal out of the fact that since they are immutable, you can validate them on creation and never worry about validation again. If the state cannot be changed, then you know it's always valid.

In which scenario can I use those design patterns in n-tier architecture? DTO is the object that you can use at the boundaries of the system. When you have a SOAP web service for example and you want to return response you would use DTO. It easier to deal with than actual XML that has to be returned over the wire. DTOs are often generated by tools, based on WSDL for example. DTO are often tailored to the needs of service consumer and can be affected by performance requirements. Value objects on the other hand live in the core of the system. It captures pieces of business logic and maybe

Let's say we have CQRS-inspired architecture, with components such as Commands, Domain Model, Domain Events, Read Model DTOs. Of course, we can use Value Objects in our Domain Model. My question is, should they also be used in: Commands Events DTOs I haven't seen any examples where Value Objects (VO) are used in the components mentioned above. Instead, primitive types are used. Maybe it's just the simplistic examples. After all, my understanding of VOs use in DDD is that they act as a glue for the whole application. My motivation: Commands. Let's say user submits a form which contains address

I'm new to DDD and NHibernate. In my current project, I have an entity Person, that contains a value object, let's say Address. Today, this is fine. But maybe one day I will have a requirement that my value object (in this case Address), will have to become an entity. Before trying to model this on a DDD-way, in a more data-centric approach, I had a table Person, with an Id, and another table Address, whose PK was actually an FK, it was the Id of a Person (ie, a one-to-one relationship). I've been reading that when I map a Value Object as a Component, its value will get mapped as columns on my