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There are a clear tendency towards the use of social Web applications (eg. Twitter, Google Reader, Waze, Facebook, etc). The analysis of the distributed flow of information in these applications is interesting nowadays, however, this analysis is complex. For example, consider that we want to analyze the popularity of a piece of news in a social Web application like Twitter. The popularity of a piece of news is measured as the number of republications of the piece of news that somebody published. For instance, consider the scenario of four people: Paul, Mike, Peter, and Kuky; where Paul published the news “There is a new version of OTM.” and other three users received this news. If Mike and Kuky republish this news, then the popularity of this news is two. Instead, if nobody republishes this news, the popularity of this news is zero. 
The following Web page shows four instantiations of a toy social Web application 1). If a user writes his name, this user is able to publish news to other users and republish news received.
NOTE: This example is incomplete!
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