Researchers in Hewlett-Packard's CoolTown research program are developing a "Websign" application for wireless devices which combines the advantages of wireless technology and ubiquitous computing "to provide a transparent linkage between the physical world and resources available on the Web." The websign technology "uses commonly available Internet-enabled wireless devices such as PDAs or smart phones equipped with client software, a positioning system such as GPS, and a digital compass to visualize services for physical entities. Devices sense physical entities in the environment and map them to a Web browser. When the user requests new information, the mobile device connects to a Web server and downloads and caches XML descriptions of websigns in a wide surrounding area. Websigns essentially bind location coordinates, control parameters such as access range, and a service represented by a URL. The Websign Markup Language (WsML), an XML application, is used to express the binding semantics: the Web servers host WsML for mobile devices to download over a cellular wireless connection. Mobile devices can also host WsML for other peer-to-peer devices. Typically, peer devices can communicate over short-range radio networks such as Bluetooth or send WsML embedded in text-message-over systems such as Short Message Service." WsML, similar to Geography Markup Language (GML), "provides a compact format for transmitting binding information over a low-bandwidth wireless network."

Details:

"Using a Web interface lets the [Websign] infrastructure remain both simple and open. The Web interface provides a geographical map as a reference for placing websigns. In the back end, a database stores the location, URL, and other binding information entered through the Web interface. When users connect to this server via HTTP and optionally post their coarse granular location to a Web server, they are served WsML based on the information in the database as well as their profile. An alternative to dynamically generating WsML is to statically create and host it on a Web server, but doing so removes the ability to personalize content."

Websign clients can either autodiscover or manually select WsML servers. The system uses information transmitted from IR or radio beacons to autoconfigure clients to communicate with known servers. Autoconfiguration is particularly useful in an enterprise scenario. For example, when employees or visitors enter a building, an IR or short-range radio message can configure their PDAs to communicate with a websign server. The PDA downloads WsML, which contains pointers to physical resources such as printers and smart conference rooms and their associated services."

For a number of reasons, the development team "chose to define a new, simple markup language instead of using the, another XML application, to bind complex geospatial areas to URLs. GML's attribute set contains complex descriptions that the websign system does not need, and it cannot meet some websign system requirements. To keep mathematical computation manageable in a PDA, for example, they bind a URL to a simple point with a surrounding square area as the access zone. Web-signs also have temporal activation parameters, which GML normally does not describe. WsML is still an evolving format, and keeping it compact requires restricting the core language to a bare minimum..."

"Websigns: Hyperlinking Physical Locations to the Web." By Salil Pradhan, Cyril Brignone, Jun-Hong Cui, Alan McReynolds, and Mark T. Smith. In IEEE Computer Volume 34, Number 8 (August 2001), pages 42-46. [Special Issue on "Location Aware Computing."]