A processing model for temporal analysis and its application to plan recognition
Fei Song · 1992
Temporal analysis is the process of extracting through linguistic analysis the temporal relations between the states and events mentioned in a discourse. We generally call these states and events situations. One main contribution in this thesis is to present a processing model for the temporal analysis of a restricted class of discourse referred to as simple narratives. Our model for temporal analysis considers the effects of tense and aspect. For tense interpretation, we present detailed rules for interpreting tense, suggest heuristics for capturing coherent tense sequences, and design a processing algorithm for determining the temporal ordering between the situations mentioned in a discourse. For aspect determination, we clearly distinguish various views of a situation, i.e., the parts of the situation described by utterances, and further present a procedure for determining the view of a situation from linguistic analysis. Tense and aspect together help decide temporal relations between situations treated as a whole. Although temporal relations have been used for plan recognition, there are no algorithms for extracting these relations from plan-based input. We apply our model for temporal analysis to plan-based input and work out a simpler and more accurate algorithm for extracting the temporal relations between the actions in a plan. We use the extracted temporal relations from temporal analysis as constraints to improve the results of plan recognition. We also use the prestored temporal constraints in the plans of the system's plan library to assist in temporal analysis. The interaction between extracted constraints and prestored constraints can be formulated as the temporal reasoning problem. We find that previous algorithms for temporal reasoning give weak results when applied to plan recognition, specifically for the case where some actions and defined in terms of their decomposed subactions. We then provide a strengthened procedure, which closes the temporal constraints between an action and its decomposed subactions. The model for temporal analysis is further defended through experiments with naturally occurring examples, and the contributions in the special case of plan-based input are made clearer by comparison to the previous work in that area.