<html xmlns="http://www.w3.org/1999/xhtml">
<head>
  <title>&lt;span&gt;</title>
</head>
<body>
  <!-- is structured inline -->
  <p><span class="class" xml:lang="en">text</span></p>

  <!-- is strictly inline -->
  <p><dfn><span class="class" xml:lang="en">text</span></dfn></p>

  <!-- can be empty -->
  <p>text <span></span></p>
  <p>text <dfn><span></span></dfn></p>

  <!-- can contain interactive -->
  <p><span><a>text</a></span></p>
  <p><dfn><span><a>text</a></span></dfn></p>
</body>
</html>