Reference to Locations

REFERENCE TO LOCATIONS Lewis G. Creary, J. Mark Gawron, and John Nerbonne Hewlett-Packaxd Laboratories, 3U 1501 Page Mill Road Palo Alto, CA 94304-1126 Abstract I.I Sketch of Proposal We propose a semantics for locative expressions such as near Jones or west of Denver, an impor- tant subsystem for NLP applications. Locative ex- pressions denote regions of space, and serve as argu- ments to predicates, locating objects and events spa- tially. Since simple locatives occupy argument posi- tions, they do NOT participate in scope ambiguities m pace one common view, which sees locatives as logical operators. Our proposal justifies common representa- tional practice in computational linguistics, account- ing for how locative expressions function anaphori- tally, and explaining a wide range of inference in- volving locatives. We further demonstrate how the argument analysis may accommodate multiple loca- tive arguments in a single predicate. The analysis is implemented for use in a database query application. 1 Introduction Locative expressions take diverse forms: in New York, here, there, nowhere, and on a boat he has in Ohio. They combine with common nouns (city on the Rhine), or with verbs or verb-phrases (work in Boston), always locating objects and situations in space. Some temporal expressions are similar, but we focus here on spatial locatives. The analysis was developed for use in an NLP sys- tem producing database queries; it is fully imple- mented and has been in frequent (developmental) use for 18 months. It is important to provide facilities for reasoning about location in database query ap- plications because users typically do not query loca- tive information in the exact form it appears in the database. A database may e.g. contain the infor- mation that a painting is in the Guggenheim Mu- seum, perhaps even that it's in the Guggenheim in New York, and yet be helpless when queried whether that same painting is in the US. In our implementa- tion information about location is represented using the logical analysis provided here. I i of course, the in£ormation that New York is in the US must be provided by a compatible geographical knowledge base. The provides general service: first, in collecting the data relevant to a semantic analysis of locatives; sec- ond, in presenting the proposal in a fashion which ap- plies to other natural languages and other logical rep- resentations; and third, in noting the consequences of our proposal for the organization of NLP systems, specifically the cooperation of syntax and semantics. The behavior of locatives in inference and anaphora reflects their semantics. This behavior justifies the hypothesis that (unquantified) locatives refer to re- gions, while related sequences of locatives refer to the intersection of the regions associated with their components. E.g. the phrase (sequence) in Canada on the Atlantic Coast refers to the (maximal) region which is both in Canada and on the Atlantic Coast. Locative adverbials within a verb phrase will then be seen to contribute to a location argument in pred- icates which identifies an area within which the pred- icate …

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