DDD, value objects and ORM

When Eric Evans talks about "entities have identity, Value Objects do not", he's not talking about an ID column in the database - he's talking about identity as a concept.

VOs have no conceptual identity. That doesn't mean that they shouldn't have persistence identity. Don't let persistence implementation cloud your understanding of Entities vs VOs.

See my post here.

As far as my understanding of DDD goes value objects are just a way to partition your entities. If a value object should be stored with an ID in the database it's not a value object.

Example:

The domain model looks like this (C#):

public class Customer : Entity
{
    public Guid CustomerID { get; }

    public string LastName { get; set; }

    public Address HomeAddress { get; set; }
}

public class Address : ValueObject
{
    public string Street { get; set; }

    public string City { get; set; }

    public string ZipCode { get; set; }
}

The corresponding database table would look something like this (Pseudo-SQL):

CREATE TABLE Customers
(
    CustomerID,

    LastName,

    HomeAddress_Street,

    HomeAddress_City,

    HomeAddress_ZipCode,
)

To store the addresses in a seperate table you would make it an entity which has an ID.