Smart space and smart appliances, i.e. wirelessly ad-hoc networked, mobile, autonomous special purpose computing devices, providing largely invisible support and context-aware services have started to populate the real world and our daily lives. In such a world, where literally everything is connected to everything with invisible, wireless data links, we need new styles on how humans and things can interact. We have proposed a spontaneous interaction'' thought model, in which things start to interact once they reach physical proximity to each other: Explained using the metaphor of an aura’’, which like a subtle invisible emanation or exhalation radiates from the center of an object into its surrounding, a digital aura'' is built on technologies like Bluetooth radio, RFID or IrDA together with an XML based profile description, such that if an object detects the proximity (e.g. radio signal strength) of another object, it starts exchanging and comparing profile data, and, upon sufficient similarity’’ of the two profiles, starts to interact with that object. A ``digital aura’’ depending on the implementation technology, is dense in the center of the object, and thins out towards its surrounding until it is no longer sensible by others. Profiles described as semi-structured data and attached to the object, can be matched by a structural and semantic analysis. Peer-to-peer concepts can then be used to implement applications on top of the digital aura model for spontaneous interaction.