based on information in the parent model.</li>
<li>When relationships are specified by ID, avoiding additional fetches
from the server for records that are already loaded.</li>
<li>Support for saving records, and tracking what exactly has changed on
your model object.</li>
<li>Support for rolling back changes that the user made since the last
fetch or save. This makes it easy to implement <code>cancel</code> buttons, for
example.</li>
<li>A well-defined separation between your model objects, how they are
fe