A System for the Semantic Interpretation of Unrestricted Domains using WordNet

In this demonstration, we show an algorithm for the semantic interpretation of unrestricted texts. The algorithm presents a solution for the following interpretation problems: determination of the meaning of the verb, identification of thematic roles and adjuncts, and attachments of prepositional phrases (PPs). An interesting aspect of the algorithm is that the solution of all these problems is interdependent. The interpretation algorithm uses WordNet (Miller et al. 1993) as its lexical knowledge-base. Predicates, or verbal concepts, have been defined for WordNet verb classes (Fellbaum 1993), which have been reorganized considerably following the criteria imposed by the interpretation algorithm. The WordNet ontology for nouns has also undergone some reorganization and redefinition to conform with the entries in the thematic roles of the predicates. We have taken a top-down approach that defines generic abstract predicates subsuming semantically and syntactically a large class of verbs. WordNet verb classes have been mapped into these generic predicates. Some of this mapping has required us to define new classes and to reclassify and/or redefine some WordNet classes and subclasses (Gomez 1998a). The predicates form a hierarchy in which thematic roles and inferences are inherited by subpredicates from their superpredicates. Two major consequences derive from anchoring verb classes in abstract semantic predicates: coalescing several WordNet senses into a predicate, which reduces the systemic polysemy in some WordNet senses, and mapping the same WordNet synset into distinct predicates. For instance, all the 5 synsets listed by WordNet for "travel": "travell, go, move, locomote;" "travel2, journey; .... travel3, take a trip, make a trip;" "travel4, journey;" and "travel5 (undergo transportation, as in vehicle)" are coalesced into the abstract semantic predicate change-of-location-by-animate. This predicate defines a class of verbs containing the most generic properties shared by all members of the class. The differentia between this predicate and its subpredicates are given by one or more of the following: a) specific selectional restrictions for the thematic roles, b) different syntactic realizations of the thematic roles, and c) specific sets of inferences associated with the subpredicates. For instance, the instrument of drive is always a vehicle, while the instrument of change-of-location-by-animate can be an animate, an animate body part, etc. The instrument of drive is never realized by a subject, but the instrument of the generic predicate can be realized by a subject, e.g., "This bus goes to Cambridge every Wednesday." On the other hand, migrate differs from change-of-location-by-animate only by the …