Pervasive Open Infrastructure

Pervasive computing provides a means of broadening and deepening the reach of information technology (IT) in society. It can be used to simplify interactions with Web sites, provide advanced location-specific services for people on the move, and support all aspects of citizens' life in the community. The Construct system identifies the best-of-breed techniques that have been successfully implemented for pervasive systems. They are collected together into a middleware platform, an intermediary between sensors and services. Construct provides a uniform framework for situation identification and context fusion, while providing transparent data dissemination and node management. Construct's basic architecture (Figure below) relies on services and sensors that access a distributed collection of nodes, which are responsible for aggregating data from the sensors. Construct regards all data sources as sensors: for example, physical ones for temperature, pressure, and location are included along with virtual ones that access digital and Web resources.

A sensor injects information into Construct's resource description framework (RDF) triple-store database. The triple store provides a set of common descriptions for concepts across domains. This model means that different sensors can be used to detect the same information. Location may be sensed directly from RFID (radio frequency identification) or Ubisense, or inferred from diary or proximity information. Yet all this information can be accessed by services using a common data model. To request information from the database, applications query the triple store using the standard SPARQL language. On the other hand, it does not provide remote access to sensors: instead, sensor data is transmitted around the network using the Zeroconf protocol for node discovery and gossiping to exchange data. Gossiping means that nodes randomly synchronise their triple stores. This can lead to substantial background communications traffic, but increases the robustness of the system, since a node failure will not cause sensed data to be lost.

More information:

http://www.perada-magazine.eu/view.php?article=1262-2008-09-22&category=Middleware