Very often, you will find yourselves having to define a certain property for an item based on its category. For example, cost($) of an item based on the size of that item (small, medium, or large). This is similar to using lookups in Excel to create a map from the size-cost table to the list of items.
This article will show you how to model such a category mapping in AIMMS.
Find a use case and more information here