As in any real object-oriented language, you can define your own class attributes. In this example, we want the size of the border in the borderedbox class to be customizable. We use the <attribute> tag to define a class attribute in borderedbox. We provide the attribute with a name (bordersize) and a default value (3). You can now use bordersize as a tag attribute to set the size of the border in instances of the <borderedbox> class.