The values of a bracket atom's element and selected attributes are determined by the symbol production ("symbol"). Three non-terminal variants are supported. These three variants influence the element and selected attributes in different The star variant leaves both attributes as their default values. The element variant assigns the element attribute to the corresponding value while leaving the selected attribute as its default value. The selection non-terminal sets the element attribute to the corresponding element and the selected attribute to true. For example, the selection sequence "p" would assign the atomic element and selected attribute to P and true, respectively.