mation, it will give your application the same record it had
provided it the first time.  This feature—always returning the same
record object, no matter how many times you look it up—is sometimes
called an <em>identity map</em>.</p>
<p>Using an identity map is important because it ensures that changes you
make in one part of your UI are propagated to other parts of the UI. It
also means that you don't have to manually keep records in sync—you can
ask for a record by ID and not have to worry about whe