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Institute of Pervasive Computing
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Digital Aura.

Funding Industrial cooperation    
Duration 2004
Consortium Johannes Kepler Universität Linz, Siemens CT SE2

"Digital Aura" proposes 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.

Key Issues

  • Spontaneous interaction among everyday objects
  • People and environments are mediated by various invisible computers in an ad-hoc style
  • Self-explaining, self-aware autonomous computing devices


  • interest and preference profile (XML)
  • proximity sensing (BT, IrDA, WiFi…)
  • "en-passant" profile exchange profile matching/similarity analysis
  • active/passive privacy control

The Digital Aura
The vision of pervasive computing tells us that the future landscape of smart appliances and smart spaces will be one in which literally "everything" is connected to "everything", interacting in a collaborative and coordinated way. A whole new class of problems related to the interaction among humans and machines comes along with this prospect, possibly better approached based on new thought models of "interaction", than based on the classical understanding of computing.

In esoterism, the aura of a person (or a thing) is "an oval shaped, etheric, subtle, invisible emanation or exhalation" that radiates from the body in a spatially limited range, dense and thick in the portion nearest the body, and thins out as distance from the body increases.

The individual "auras" of persons or things can be built on the proximity area of a wireless sensor node, determined from the received radio signal strength (or the signal to noise ratio, SNR), as available from many wireless MAC layers for technologies like Bluetooth, RFID or IrDA. In our approach, a self-describing interest profile, encoded in XML, is being attached to each individual object, and exchanged among objects that have approached physical proximity to each other. This whole concept of spontaneous interaction based on the metaphor of a "digital aura" has been implemented in the SILICON P2Pcomp software framework.

The Digital Aura identifies matching interest
Alice, a student, looks for help with pattern recognition algorithms for her algorithms class. She encodes a request for help in her interest profile, stored on her Bluetooth enabled PDA. As she walks around the university campus (a), Bob, a PhD student and expert in algorithms, passes by (b). His Bluetooth enabled smart phone recognizes and alerts him Alice’s request (c). He dials the mobile phone number that has been transferred with Alice’s profile to his smart phone (d), and the two get in contact.