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