Reconciliating divergent data is an important issue in concurrent engineering, mobile computing and software configuration management. Currently, a lot of synchronizers or merge tools perform reconciliations. However, they do not define what is the correctness of their synchronisation. In this paper, we propose to use a transformational approach as the basic model for reasonning about synchronisation. We propose an algorithm and specific transformation functions that realize a file system synchronisation. Unlike classic synchronizers, our synchronizer ensures properties of convergence, causality and intention preservation and is extensible to new data types.