Research Professor at Carnegie Mellon University on leave, and now as Chief Technologist at Seagate Technology. I occasionally tweak Wikipedia when I see something I believe really needs tweaking, like causality. I've been reachable as rht@cs.cmu.edu since the early 1980s, and from nearly any network since 1988. One of the first two dozen or so web pages at CMU at http://www.cs.cmu.edu/~rht