The web is no longer perceived as a documentary system built on a simple protocol (HTTP), a simple addressing scheme (URI) and a simple document formatting language (HTML). It grew to become a huge network of distributed data, applications and users where many flows of heterogeneous messages travel. The web is an object of science: it is a very complex system that requires a multidisciplinary scientific approach. Our institutes are more and more solicited to understand how these data and interactions can be processed, supported, controlled, exploited or improved.