Judging by the papers, it looks like it was mainly active from 1994 to around 2000-2001 or so. Although there is also a 2005 journal article: http://dl.acm.org/

Judging by the papers, it looks like it was mainly active from 1994 to around 2000-2001 or so. Although there is also a 2005 journal article: http://dl.acm.org/citation.cfm?id=1075385 http://dl.acm.org/citation.cfm?id=1075385