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So how do we create physical hyperlinks. Our first solution was an infrared beacon, consisting of a small circuit board, a PIC processor, an infrared transceiver, and a battery. The assembly is a bit bigger than a large watch. Every 3 seconds the processor pumps 138 bytes out in a single IR packet that irradiates a cone 30 degrees wide by one meter long. The packet conforms to a little used IRDA subprotocol called “ultra” that resembles UDP packets. The result is a “localcast” which we use to hold a URL. If the beacon is mounted on the wall of a seminar room and if the URL broadcast points to a resource for the room, presto you have a physical hyperlink for the room.
For more information on the beacons, please visit our web site at

We have been experimenting with other hyperlinking technologies. Using a simple barcode or RFID tag we can get a long number; by passing the long number into a lookup service something like DNS in reverse we get a URL. These lookup based tags give us a point of indirection for configuration of a system of tags as well as the potential for lower cost and lower maintenance; they do require deployment of the lookup service.
For more information on WebID please read the paper by Tim Kindberg on ubiquitious object identifiers.
The paper can be located by typing “ubiquitious Tim Kindberg” into google.
Tag URIs (Tim Kindberg and Sandro Hawke) -- a new type of URI that enables anyone who currently holds an email address or a domain name to construct a resource identifier that is guaranteed to be unique for all time. See draft-kindberg-tag-uri-01.txt.
Ubiquitous and contextual identifier resolution for the real-world wide web (Tim Kindberg). HP Labs Tech. report HPL-2001-95.