All objects in the system have properties such as name, date of creation, size, color, and so forth. A group of like objects make up a class. The objects in one class differ from the objects in another class by their properties. If a class is descended from another class, however, the objects from the descended class have, at least, all the properties of its parent, and can have some of their own. The following figure shows the Add Criteria dialog:

To create a valid criteria, four elements must be specified: