ore types and an extended set of Activity and Object types common
      to many social Web applications. The core types include:
      <ul>
        <li><a>Object</a>,</li>
        <li><a>Link</a>,</li>
        <li><a>Activity</a>,</li>
        <li><a>IntransitiveActivity</a>,</li>
        <li><a>Collection</a>,</li>
        <li><a>OrderedCollection</a>,</li>
        <li><a>CollectionPage</a>, and</li>
        <li><a>OrderedCollectionPage</a>.</li>
      </ul>
    </p>

    <p>
      Every JSON object in an 