Web Services are a promising future for distributed computations on the net. So far there has been much speculation. But to develop anything nontrivial presents a severe problem to programmers. It is hard to simulate a large, multigigabyte database, that has credible applications.
Luckily, two successful Internet companies, Google and Amazon, have done so. They offer access to their data via XML queries. The authors thus explain how you can sign up with these companies and use their Web Services as a testbed. They treat each company separately and show examples of how you can mine the data and possibly integrate it with your own data and display the results, typically in a browser fashion.
The companies are used as learning examples, since many of you are likely to have already used their regular browser based offerings. The authors use this familiarity to motivate why and how you can get at the data, without all that HTML clutter of a pre-Web Service screen scraping approach. They also use this as a vehicle to explain how to use DOM, SOAP, XSLT and JSPs on your website, as part of your Web Service. Tomcat is chosen as the web container because it is very stable and, let's face it, free. So you do gain fluency in an impressive number of important packages.
They even offer examples of how to use DAV. This, in the 10 year history of the web, refers to distributed authoring. It was present in the http specifications of 1992/3. But this has rarely been implemented in browsers or http servers ever since. A backwater that is now starting to attract attention. Especially when recast in the rubric of Web Services.