The university campus is an interesting application environment for the ubiquitous computing paradigm: a large number of users share a substantial amount of their information needs and much of this information is directly related to physical objects, places, and people that are situated in the campus environment. We motivate the need for material entry points into a virtual campus that increase its accessibility and visibility from within the physical campus environment.

We focus on the aspect of linking virtual and physical elements in such a setting and present the ETHOC system, which enables users to attach virtual counterparts to printed material. The system performs the creation, administration, and intermediation of online resources related to paper documents. To information providers, it offers a Web-based author portal for generating unique IDs that can be printed as barcodes and for associating online content and actions to printed material. To users it offers simple means to interact with virtual counterparts of printed documents using a variety of devices, such as WAP-enabled mobile phones or PDAs, and it stores a personal access history for each user.

The ETHOC system allows us to put ubiquitous computing concepts into practical use and to gain new insights into the design of virtual counterparts of real-world objects.