for discussions and advice. I would like to thank Arnaud Durand and Patrice Ossona de Mendez for accepting to review this thesis and for their constructive comments on the earlier versions of this manuscript. Many thanks to Nicole Bidoit and Victor Vianu for accepting to be in my jury. Special thanks go to my

distributed XML T3.2 Compile time analysis T3.3 Run time analysis Task T3.2 and T3.3 will start only at M19. Task T3.1 started at M6, and therefore only last for six months. Main results. There were two main results. The first main result is the work of Serge Abiteboul, Pierre Bourhis and Victor Vianu

The Webdam ERC grant is a five-year project that started in December 2008. The goal is to develop a formal model for Web data management that would open new horizons for the development of the Web in a well-principled way, enhancing its functionality, performance, and reliability. Specifically, the goal is to develop a universally accepted formal framework for describing complex and flexible interacting Web applications featuring notably data exchange, sharing, integration, querying, and updating. We also propose to develop formal foundations that will enable peers to concurrently reason about global data management activities, cooperate in solving specific tasks, and support services with desired quality of service. Although the proposal addresses fundamental issues, its goal is to serve as the basis for future software development for Web data management.

We study highly expressive query languages for unordered data trees, using as formal vehicles Active XML and extensions of languages in the while family. All languages may be seen as adding some form of control on top of a set of basic pattern queries. The results highlight the impact and interplay of different factors: the expressive power of basic queries, the embedding of computation into data (as in Active XML), and the use of deterministic vs. nondeterministic control. All languages are Turing complete, but not necessarily query complete in the sense of Chandra and Harel. Indeed, we show that some combinations of features yield serious limitations, analogous to FO k definability in the relational context. On the other hand, the limitations come with benefits such as the existence of powerful normal forms. Other languages are “almost ” complete, but fall short because of subtle limitations reminiscent of the copy elimination problem in object databases.