The essential construction of Visual Who lists all the names in the virtual community and then calculates the level of attachment of those names to certain mailing lists, the theory being that mailing list participation is a strong reflection of role identity at the MITMediaLab. The final placement on the screen of a name is determined by the summation of springs attached from the mailing list anchors to the names. Colours of the names reflect roles (faculty, staff, students, etc.). Brightness indicates involvement. The process is dynamic, so the operator can derive information from the motion as well as the differences between adding an anchor or removing it or moving it around.
Finally, the system can also limit names to those currently logged in to give a sense of the current activity of the system. The paper does not describe any practical gain from this limitation.
See also JudithDonath's later stunning work ChatCircles.
Donath, J. (1995) Visual Who. in ACM Multimedia 95 - Electronic Proceedings, November 5-9, San Francisco, California. Available from http://smg.media.mit.edu/people/Judith/VisualWho/VisualWho.html