Like most non-trivial GWT applications, both the Address Book and Yahoo! Trips applications use remote procedure calls to access information on the server. For example, when the Address Book application starts up, it makes an RPC to the server to load contacts from a database.
The Yahoo! Trips application also uses RPCs, but it uses them to access an online web service instead of a database. Figure 2 shows the Yahoo! Trips web site, where people can post information about their trips, which other people can access through a search. If you were planning a vacation to Paris, for example, you could look at other people’s Paris trips for some good ideas.