Participated in the ARPA-sponsored "summer study group" that kicked off Project MAC at MIT. Wrote a project memo about the dichotomy between "User System" and "Service System." Essentials are described in Rpt-65C, and the expanded dichotomy recurs as for instance in Pub-73-AKW ,Pub-78-IntEvolOAS and Pub-82-HiPerfKW. Had my turn to address the whole group (50 or so people); not much reaction, but I do remember the group hoot when I said that we'd all be seeking to boost response time for many man-computer interactions down to at least a quarter of a second before the returns began to diminish.