This examples goes even further on directive cooperation. Until now, we connected directives sharing a tag. AngularJS makes it possible to connect directives at different levels:

<ul fa-select="selection">
  <li><input type="checkbox" fa-select-option></li>
  <li><input type="checkbox" fa-select-option></li>
  <li><input type="checkbox" fa-select-option></li>
</ul>

The <fa-select> directive exposes a controller that is required by all child <fa-select-option>. It gathers the list of currently selectioned options. This is done by passing '^' to require (to search a matching controller on parent tags).