Well, there goes another chapter. Chapter 6 is all about data.
"Dynamic data is an important part of any Palm webOS application to keep the user connected and in touch, while local data is critical for offline access and a responsive user experience. In this chapter, we've covered both topics, showing you how to use the Depot and Cookie objects, along with Prototype's Ajax functions and the HTML 5 Database APIs to provide what you need. Managing your data in an efficient way is as fundamental to a great user experience as the powerful UI functions."
http://www.prethinking.com/home/2009/5/10/webos-book-chapter-6-data-mojo-cookies.html