Home >Online Product Documentation >Table of Contents >Specifying That an Element is Optional in DTDs
You specify that an element is optional when you add a reference to that element in another element. When an element is optional, it means that there can be one or none. If you want to specify that there can be none, one, or more, use the Zero or More modifier. See Specifying That Multiple Instances of An Element Are Allowed in DTDs.
After you add a reference to an element, you might want to check the definition of the referenced element. To do this, right-click the reference. In the shortcut menu, click Go To Definition. Stylus Studio moves the focus to the definition of the referenced element.