For a categorical attribute, we can have a multiway split, with a child for
each value of the attribute. This works fine for categorical attributes with only
a few distinct values, such as degree or gender. However, if the attribute has
many distinct values, such as department names in a large company, creating a
child for each value is not a good idea. In such cases, we would try to combine
multiple values into each child, to create a smaller number of children. See the
bibliographical notes for references on how to do so.