Your Homepwner application currently uses archiving to save and reload its data. For a moderately sized object model (say, fewer than 1000 objects), this is fine. As your object model gets larger, however, you will want to be able to do incremental fetches and updates, and Core Data can do this.
The very first step is to add the Core Data framework to your project. Select the Homepwner target and under Build Phases, open the Link Binary With Libraries build phase. Click the + button to add the Core Data framework.
Figure 16.1 Add Core Data framework
In a relational database, we have something called ...