page_title: Object hyperlinking
section_title: Tags and tag-reading systems
hierarchical_section_title: Object hyperlinking / Tags and tag-reading systems
context_page_description: Object hyperlinking, or simply 'phylinking', is a neologism that usually refers to extending the Internet to objects and locations in the real world. The current Internet does not extend beyond the electronic realm. Object hyperlinking aims to extend the Internet to the physical world by attaching tags with URLs to tangible objects or locations. These object tags can then be read by a wireless mobile device and information about objects and locations retrieved and displayed.
  However, object hyperlinking may also be sensible for contexts other than the Internet.
context_section_description: There are a number of different competing tagging systems.
  RFID tags
  A radio frequency identification device (also known as an 'Arphid') is a small transponder which can be read at short range by a transceiver (reader). Since RFID tags can be very small, they are often embedded in a more visible marker to allow them to be located.
  A RFID reader can be added to an existing mobile telephone as a shell. Nokia produce such a shell for their 3220 mobile phone. More and more mobile phones have RFID/NFC capability, since such RFID/NFC enabled mobiles may be used for cashless payments and other purposes.
  Since 2005 travelers in the city of Hanau, near Frankfurt, Germany have been able to pay for bus tickets by passing their Nokia phones over a smartcard reader installed on the buses. Other applications for RFID enabled mobiles include swapping electronic business cards between phones, and using a mobile to check in at an airport or hotel. Two RFID enabled devices may also be used to enable peer-to-peer transfer of data such as music, images or for synchronizing address books.
  Graphical tags
  A graphical tag consists of an image on a marker, which can be read by a mobile telephone camera. There are a number of competing systems, including open standards like Quick Response QR Codes, Datamatrix, Semacodes (based on Datamatrix), and barcodes; or proprietary systems like ShotCodes. The design of such coding schemes needs to be rich enough to include much information and robust enough for the tag to be readable, even when partly obscured or damaged: tags might be on the outside of buildings and exposed to wear and the weather.
  Graphical tags have a number of advantages. They are easy to understand and cheap to produce. They can also be printed on almost anything, including t-shirts. Barcodes are a particularly attractive form of tagging because they are already very widely used, and camera phones can easily read them.
  SMS tags
  An SMS tag comprises a short alphanumerical code, which can be printed on a marker or chalked on a wall. The Short Message Service is then used to send the code and return a message. Yellow arrows are an example of this form of tagging.
  Virtual tags
  In a virtual tagging system there is no physical tag at a location. Instead a URL as a meta-object is associated with a set of geographical coordinates. Using location-based services a mobile phone  that enters a particular area can be used to retrieve all URLs associated with that area. The area can be set as a few metres or a much wider area.
  Hardlink
  A hardlink is an alphanumeric combination such as an object's common name or part number that when entered into a cell phone's web browser, targeting a hardlink database, returns information that may have been stored about the target object.
caption: QR Code for "An Internet of Things" "
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