/pre>
</div>
</figure>

      <p>
        While implementations are free to introduce new types of Actors beyond
        those defined by the Activity Vocabulary, interoperability issues can
        arise when applications rely too much on extension types that are not
        recognized by other implementations. Care should be taken to not unduly
        overlap with or duplicate the existing Actor types.
      </p>
      <p>
        When an implementation uses an extension type that overlaps with a core
  