title: Why use Schema.org microdata to mark up web page elements?
body: <p>I understand why and how to use <a href="http://schema.org/" rel="nofollow">Schema.org</a> to add microdata to your site, this is not a question about that. The question is <em>why Schema.org has support for certain things that can be marked up with simple HTML5</em>. Among these are</p>
  
  <p><strong>Types</strong></p>
  
  <ul>
  <li><p><a href="http://schema.org/WebPage" rel="nofollow">WebPage</a> and <a href="http://schema.org/WebSite" rel="nofollow">WebSite</a></p>
  
  <p>I can see why <code>WebPage</code> and <code>WebSite</code> would be needed, for example, to reference the page/site of a certain organization in a link, but there's no need to mark up your own page with this&mdash;the <code>&lt;html&gt;</code> tag does this.</p></li>
  <li><p><a href="http://schema.org/SiteNavigationElement" rel="nofollow">SiteNavigationElement</a></p>
  
  <p>Why not just use <a href="http://www.w3.org/TR/html5/sections.html#the-nav-element" rel="nofollow"><code>&lt;nav&gt;</code></a>?</p></li>
  <li><p><a href="http://schema.org/Table" rel="nofollow">Table</a></p>
  
  <p>Just use <a href="http://www.w3.org/TR/html5/tabular-data.html#the-table-element" rel="nofollow"><code>&lt;table&gt;</code></a>.</p></li>
  </ul>
  
  <p><strong>properties</strong></p>
  
  <ul>
  <li><p><a href="http://schema.org/mainContentOfPage" rel="nofollow">WebPage/mainContentOfPage</a></p>
  
  <p><a href="http://www.w3.org/TR/html5/grouping-content.html#the-main-element" rel="nofollow"><code>&lt;main&gt;</code></a> element</p></li>
  <li><p><a href="http://schema.org/relatedLink" rel="nofollow">WebPage/relatedLink</a></p>
  
  <p><a href="http://www.w3.org/TR/html5/document-metadata.html#the-link-element" rel="nofollow"><code>&lt;link&gt;</code></a> element inside <code>&lt;head&gt;</code></p></li>
  </ul>