Marc Shapiro is a director of research with INRIA and the chairmain of Eurosys, the ACM SIGOPS chapter of Europe. He is going to give a talk in today's systems lunch: Speaker: Marc Shapiro, INRIA and LIP6 Title: Telex: A Principled Platform for Peer-to-Peer Collaboration Abstract: Developers of co-operative applications encounter difficult issues of distributed state, disconnections, and conflicts. Our approach is to factor these system issues out from application logic, but we recognise that they cannot be entirely divorced. The Telex platform that we designed is application-independent, but parameterised by application-specific information. An application provides Telex with actions (operations) and constraints (invariants). In return, Telex takes care of replication and persistence, drives application progress while verifying its invariants, and ensures that replicas eventually agree on a correct, common state. Time permitting, I will present a number of contributions. I show by example how application design proceeds from high-level invariants to actions and constraints, and how the platform ensures application safety and liveness. The main data structure of Telex is a large, replicated, very dynamic graph; I discuss the engineering trade-offs for such a graph and our solutions. I describe our how Telex ensures, in the background, that replicas converge to a safe state. Finally, I describe experimental evaluation of the Telex platform. Joint work with Lamia Benmouffok, Jean-Michel Busca, Joan Manuel Marquhs, Marc Shapiro, Pierre Sutra, Georgios Tsoukalas