Conceptual metaphor and scripts in Recognizing Textual Entailment

The power and pervasiveness of conceptual metaphor can be harnessed to expand the class of textual entailments that can be performed in the Recognizing Textual Entailment (RTE) task and thus improve our ability to understand human language and make the kind of textual inferences that people do. RTE is a key component for question understanding and discourse understanding. Although extensive lexicons, such as WordNet, can capture some word senses of conventionalized metaphors, a more general capability is needed to handle the considerable richness of lexical meaning based on metaphoric extensions that is found in common news articles, where writers routinely employ and extend conventional metaphors. We propose adding to RTE systems an ability to recognize a library of common conceptual metaphors, along with scripts. The role of the scripts is to allow entailments from the source to the target domain in the metaphor by describing activities in the source domain that map onto elements of the target domain. An example is the progress of an activity, such as a career or relationship, as measured by the successful or unsuccessful activities in a journey towards its destination. In particular we look at two conceptual metaphors: IDEAS AS PHYSICAL OBJECTS, which is part of the Conduit Metaphor of Communication, and ABSTRACT ACTIVITIES AS JOURNEYS. The first allows inferences that apply to physical objects to (partially) apply to ideas and communication acts (e.g., "he lobbed jibes to the comedian"). The second allows the progress of an abstract activity to be assessed by comparing it to a journey (e.g., "his career was derailed"). We provide a proof of concept where axioms for actions on physical objects, and axioms for how physical objects behave compared to communication objects, are combined to make correct RTE inferences in Prover9 for example text-hypothesis pairs. Similarly, axioms describing different states in a journey are used to infer the current progress of an activity, such as whether it is succeeding (e.g., "steaming ahead"), in trouble (e.g., "off course"), recovering (e.g., "back on track"), or irrevocably failed (e.g., "hijacked").