As mentioned in Chapter 12, one of the reasons Adobe Air was chosen for the sample project is its embedded database system called SQLite (see http://www.sqlite.org/). SQLite stores its data in files on the local hard drive. In the sample application, this is the FlexBlog.db file. If you open this file in Flex Builder you will see that parts of it are readable, while others look like gibberish. This is okay, as you will not be editing this file directly. Rather, you will be using the AIR API to modify this file via your code. The AIR classes for working with SQLite are located in the flash.data package, the documentation for which can be found here: http://livedocs.adobe.com/flex/3/langref/flash/data/package-detail.html.
As the purpose of the backend system is to give you a more realistic experience working with Cairngorm in the sample application (within the limitations discussed in Chapter 12) and not to have you learn the specifics of working with SQLite (or even Adobe AIR), a couple of classes have been included with the sample application (discussed in more detail in the next section) that will take care of the details of accessing the database.