Let's make persistent object Book with fields Title, Author and UserID (unique ID of user who borrowed this book).
Now you can do it easy by yourself, but if you have any problems, return and look here for each step: Persistent Object LibraryUser
This is what you should have if you did everything right:
public class Book extends DBPersistentObject { public void define() {
addField("Title", new VarcharField(50));
addField("Author", new VarcharField(50));
addField("UserID", new IDField());
}
}