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

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

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

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