Vicinity and Metrics

The term vicinity is at the core of the CoBrow service. It describes the fact that several users are temporarily close to each other in the Web. The degree of closeness is mesasured with metrics. One such metric is the number of links between the pages viewed by two users at the same time. If the users are on the same page, their distance is 0, if one or the other would have to follow 2 links to be on the same page, their distance is 2. Other metrics are time or document content.

The Web is the base infrastructure of the virtual world. It is depicted as 2 dimensional hyperspace although it is actually a graph. The left side shows a simplistic representation of two persons at different locations. The right side shows the values of the persons' visibility functions. Persons see each other if the visibility overlaps.

The CoBrow System

CoBrow consists of many functional entities. The core functionality is built on the Vicinity Evaluator, also referred to as the CoBrow server, which is typically co-located with a WWW-server. Based on location information, it calculates the vicinity of all users according to one or more metrics. The Vicinity Evaluator is probably the most complex CoBrow component. This is not only because it has to deal with a vast amount of data. There will be many Vicinity Evaluators in the Internet - CoBrow is a fully distributed service.

All Vicinity Evaluators communicate with each other to exchange information on Web users using an http-compliant protocol. The inter-Vicinity Evaluator communication is entirely transparent to the CoBrow clients. For the client software it is only one CoBrow service which is actually provided by many interactive Vicinity Evaluators.

The vicinity visualization is presented to the user by CoBrow clients. Today CoBrow clients are implemented as Java-applets, downloaded into the browser software as soon as a user enters a CoBrow-enabled server.

These clients serve as user interfaces not only to show the user where he is and who his neighbors are, but also to configure the vicinity calculation, and to start external communication tools. A VRML-based client with advanced vicinity visualization techniques is under development.

Synchronous Communication tools can be started and controlled from CoBrow. They are however not an integral component of CoBrow. CoBrow is able to use many different synchronous communication tools such as the MBone tools, the WebMedia toolkit, and CUSeeMe. An interface to the plain old telephone system and ISDN is under development.