Many-to-many mapping with extra columns in join table

Question

Here is the domain that I wish to have:

public class Person
{
    public int Id { get; set; }
    public IList AcquiredCertificates {          


        

Answer 1

Your implementation is exactly correct. Your join table includes the two key fields (making a composite primary key for the table) and the datetime field is superfluous to that. It is in fact an extra attribute on the join table and for that you need an entity.

On a UML class diagram it would show up as an attribute on the join too.