A method (and corresponding equipment and computer programs) by which a first and second device (11 12) synchronize how data is organized as folders in respective first and second data stores (11c 12c) maintained by the devices (11 12) based on exchanging messages (21) including data identification elements (28 29) that refer to the folders, with the data identification elements (28 29) provided in the message external to any reference to data units; or, more generally, based on the first device sending a message to the other and including in the message information about data in the first data store and also information about a change in the data structure of the first device, wherein the information about the data in the first data store is placed in the message in an element different from the element where the information about a change in the data structure is placed.