Looking for n-ary relationships

Sometimes, you will find that the first reading of your user stories will not yield optimal results. There can be many reasons for this, but this is often because there are some hidden model elements in these stories that we did not spot at first.

One of the cases where we often see this is when dealing with the so-called n-ary relationships. These types of relationships are often hidden in the model when we want to associate more than two things; in some cases, the natural and convenient way to represent certain concepts is to use relations to link a concept to more than just one concept. These relations are called n-ary relations because they can serve more than two (in fact, n) things or concepts. It is a very common modeling pattern.

When we discover these types of relationships in a graph model, this typically means that there's an additional node to discover that we have split out a new entity, as illustrated here:

This is exactly what we have done in the preceding example.