Decentralised systems made of autonomous devices and software are gaining more and more interest. These autonomous el ements usually do not know each other in advance and act without any central control. They thus form a society of devices and software, and as such need: basic interaction mechanisms for understanding each other and a social infrastructure supporting interactions taking place in an uncertain environment. In an effort to go beyond pre-established communication schema and to cope with uncertainty, this paper proposes an interaction mechanism based exclusively: on semantic information expressed using specifications, and on a social infrastructure relying on trust and reputation.