Browse Reports

The process of adding to the common ground between conversational participants (called grounding) has previously been either oversimplified or studied in an off-line manner. This dissertation presents a computational theory, in which a protocol is presented which can be used to determine, for any given state of the conversation, whether material has been grounded or what it would take to ground the material. This protocol is related to the mental states of participating agents, showing the motivations for performing particular grounding acts and what their effects will be. .pp We extend speech act theory to account for levels of action both above and below the sentence level, including the level of grounding acts described above. Traditional illocutionary acts are now seen to be multi-agent acts which must be grounded to have their usual effects. .pp A conversational agent model is provided, showing how grounding fits in naturally with the other functions that an agent must perform in engaging in conversation. These ideas are implemented within the TRAINS conversation system. .pp Also presented is a situation-theoretic model of plan execution relations, giving definitions of what it means for an action to begin, continue, complete, or repair the execution of a plan. This framework is then used to provide precise definitions of the grounding acts in terms of agents executing a general communication plan in which one agent must present the content and another acknowledge it.