  A robot's ability to understand or ground natural language instructions is
fundamentally tied to its knowledge about the surrounding world. We present an
approach to grounding natural language utterances in the context of factual
information gathered through natural-language interactions and past visual
observations. A probabilistic model estimates, from a natural language
utterance, the objects,relations, and actions that the utterance refers to, the
objectives for future robotic actions it implies, and generates a plan to
execute those actions while updating a state representation to include newly
acquired knowledge from the visual-linguistic context. Grounding a command
necessitates a representation for past observations and interactions; however,
maintaining the full context consisting of all possible observed objects,
attributes, spatial relations, actions, etc., over time is intractable.
Instead, our model, Temporal Grounding Graphs, maintains a learned state
representation for a belief over factual groundings, those derived from
natural-language interactions, and lazily infers new groundings from visual
observations using the context implied by the utterance. This work
significantly expands the range of language that a robot can understand by
incorporating factual knowledge and observations of its workspace in its
inference about the meaning and grounding of natural-language utterances.
