Selecting Properties 2
As you can see, we have included six properties. Most of these are obvious, but two deserve a bit more discussion.
The Category->CategoryName property is an example of a cross-class reference. Recall that Category is the name of the property we added to the Film class that refers to the FilmCategory class. CategoryName is a property in the FilmCategory class. Altogether, this compact syntax says “follow the Category reference from the Film class to the FilmCategory class and get the CategoryName”.
The other interesting property is %ID, which represents the unique identifier for a film. We will use that later, when we add a button to our Web page. Note that %ID is not a “real” column in the traditional sense; You can think of it as a special SQL operator that returns the Object Identity value for a given row.