To add another topic at the same level, repeat the same element.
Or, to add a subtopic (a topic one level deeper in the hierarchy), use the element that is one level deeper than the preceding topic.
If the current topic is an <s1>, enter a subtopic using <s2>.
<s1 id=getting-started> Getting Started <s2 id=starting-the-program> Starting the Program Here's the body of the first subtopic. <s2 id=stopping-the-program> Stopping the Program Here's the body of the second subtopic.
The second <s2> is also a subtopic of the <s1>.
Sometimes a parent-child-sibling metaphor is used to describe the relationships between topics in a hierarchy. In the preceding example, the <s1> topic is the "parent" of both <s2>s (the "children" topics). The two <s2>s are "siblings" of one another. All three topics are "descendents" of the home topic.