This page gives a brief description of what was going on 'behind the scenes' during the Preview Day on Wednesday 18th June.

The following diagram gives a conceptual overview of the make-up of the system.

Various different software components were running on a number of computers and servers, communicating via the elvin [1] content based messaging system. This allows software clients to "subscribe" to receive particular types of message, and to "publish" messages themselves.

Each time an iButton was docked or un-docked, a notification was broadcast detailing the id and location of that iButton, along with whether it was an arrival or departure.

A number of "process control" clients listen for these notifications and fire off events when they are received. For example, one client listens for arrivals and departures and logs these by asserting them as RDF [2] into the triplestore [3]. Another client queries the triplestore to retrieve further information about the person who has arrived or departed, which is then re-broadcast as another notification and in turn used by the applications.

Finally, the Preview Day Website [4] queries the triplestore to determine which of the demonstrations you visited, and uses a link server [5] to generate a personalised page detailing further information relating to those demonstrations.

Relevant links --