class MyObject{
  public String Name;
  public String Value;
}
//Mapping
Id(x => x.Name)
  .Length(255)
  .Unique();
Map(x => x.Value);

class ObjectHolder{
  public UInt64 Id;
  public ICollection<MyObject> MyObjects;
}
//Mapping
Id(x => x.Id)
  .GeneratedBy.Native();
HasManyToMany(x => x.MyObjects)
  .AsSet()
  .Cascade.SaveUpdate();

class MyObject{
  public UInt64 Id;
  public String Name;
  public String Value;
}
//Mapping
Id(x => x.Id)
  .GeneratedBy.Native();
Map(x => x.Name)
  .Length(255)
  .Unique();
Map(x => x.Value);