Mashups are Web applications that integrate and combine data from multiple Web sources to present them in a new way to a user. This chapter shows two different ways to construct mashup applications in practice: Yahoo! Pipes, a graphical user interface for building mashups, and XProc, a W3C language for describing workflows of transformations over XML documents. Pros and cons of either approach will be made clear as one follows the indicated steps. The goal will be to present information about news events, each event being accompanied by its localization displayed on a map. For that purpose, we integrate three sources of information:

1. A Web feed about current events in the world, in RSS format (e.g., CNN's top stories at http://rss.cnn.com/rss/edition.rss). Any such RSS feed is fine, though English is preferable to ensure precision of the geolocalization.

2. A geolocalization service. We use information from the GeoNames geographical database, and specifically their RSS to Geo RSS converter, whose API is described at http://www.geonames.org/rss-to-georss-converter.html.

3. A mapping service. We use Yahoo! Maps.

YAHOO! PIPES: A GRAPHICAL MASHUP EDITOR

Yahoo! Pipes allows creating simple mashup applications (simply called pipe) using a graphical interface based on the construction of a pipeline of boxes connected to each other, each box performing a given operation (fetching information, annotating it, reorganizing it, etc.) until the final output of the pipeline. It can be used by nonprogrammers, though defining complex mashups still requires skill and experience with the platform.