As we have seen, it was not very difficult to make Display capable of handling references to related entities. These relations, however, are limited to lookup relations (also known as many-to-one relations). A Contact entity, for example, refers to, at most, a single Account entity and the Display class allows us to select an Account when we edit a Contact.

But what do we need for the opposite situation? An Account may have many Contacts and both Account and Contact may have many Addresses. What we need is a way to make Display show which one-to-many relationships exist for an entity and provide the means to show those entities when the user clicks on such a relation.