ce</code>, or
<code>LineItem</code>.</p>
<p>Models tend to be <em>persistent</em>. That means the user does not expect
model data to be lost when they close their browser window. To make sure
no data is lost, if the user makes changes to a model, you need to store
the model data somewhere that it will not be lost.</p>
<p>Typically, most models are loaded from and saved to a server that uses a
database to store data. Usually you will send JSON representations of
models back and forth to an HTTP server that y