WOOT is a new distributed algorithm to collaboratively edit a linear structure. This algorithm can be deployed on a P2P overlay network since its time and space complexity is polynomial and does not depend on the number of editing sites. In this presentation, we will focus on our use of model checking method to verify correctness of the algorithm in terms of benefit and limitations. We will also present the main open issues (hierarchical structures, access control, ...) in P2P collaborative editing and our expectations about automated formal methods' help on these issues.