  We consider the design space available for social robots in terms of a
hierarchy of functional definitions: the essential properties in terms of a
locus of interaction, autonomy, intelligence, awareness of humans as possessors
of mental state, and awareness of humans as social interactors. We also suggest
that the emphasis on physical embodiment in some segments of the social
robotics community has obscured commonalities with a class of agents that are
identical in all other respects. These definitions naturally suggest research
issues, directions, and possibilities which we explore. Social robotics also
lacks compelling 'killer apps' which we suggest would help focus the community
on a research agenda.
