Many data sources on the Web evolve in the sense that they change their content over time, typically as a reaction to some event. Such changes often need to be mirrored in data on other Web nodes: updates need to be propagated. To respond to the need for evolution and reactivity both locally and globally, the language XChange has been developed. In this work, we demonstrate its applicability to a concrete scenario of distributed Web sites of a scientific community with mutual data dependencies.