  We present a system that produces sentential descriptions of video: who did
what to whom, and where and how they did it. Action class is rendered as a
verb, participant objects as noun phrases, properties of those objects as
adjectival modifiers in those noun phrases, spatial relations between those
participants as prepositional phrases, and characteristics of the event as
prepositional-phrase adjuncts and adverbial modifiers. Extracting the
information needed to render these linguistic entities requires an approach to
event recognition that recovers object tracks, the trackto-role assignments,
and changing body posture.
