Disamibiguating and Interpreting Verb Definitions

DISAMBIGUATING AND INTERPRETING VERB DEFINITIONS Yael Ravin IBM T.J. Watson Research Center Yorktown Heights, New York 10598 e-mail:Yael@ibm.com ABSTRACT To achieve our goal of building a compre- hensive lexical database out of various on-line resources, it is necessary to interpret and disambiguate the information found in these resources. In this paper we describe a Disambiguation Module which analyzes the content of dictionary dcf'mitions, in particular, definitions of the form to VERB with NP". We discuss the semantic relations holding be- tween the head and the prepositional phrase in such structures, as wellas our heuristics for identifying these relations and for disambiguating the senses of the words in- volved. We present some results obtained by the Disambiguation Module and evaluate its rate of success as compared with results ob- tained from human judgements. INTRODUCTION The goal of the Lexical Systems Group at IBM's Watson Research Center is to create COMPLEX, "a lexical knowledge base in which word senses are identified, endowed with appropriate lexical haforrn, ation and properly related to one another" (Byrd 1989). Information for COMPLEX is derived from multiple lexical sources so senses in one source need to be related to appropriate senses in the other sources. Similarly, the senses of def'ming words need to be disambiguated relative to the senses supplied for them by the various sources. (See Klavans et al, 1990.) Sense-disambiguation of the words found in dictionary entries can be viewed as a sub- problem of sense-disambiguation of text corpora in general, since dictionaries are large corpora of phrases and sentences exhibiting a variety of ambiguities, such as unresolved ?ro- nominal references, attachment ambigutties, and ellipsis. The resolution of these ambiguity problems in the context of dictionary defi- nitions would directly benefit their resolution in other types of text. In order to solve the ~roblem of lexical ambiguity in dictionary de- fruitions, we are investigating how to auto- maticaUy analyze the semantics of these definitions and identify the relations holding between genus and differentia. This paper concentrates on one aspect of the task - the semantics of one class of verb definitions. I. DISAMBIGUATING DEFINITIONS We have chosen to concentrate initially on definitions of the tbrm 'to VERB with NW in Webster's 7th New Collegiate Dictionary (Merriam 1963; henceforth W7). Disambiguating these definitions consists of identifying the appropriate sense of 'with (that is, the type of semantic relation linking the VERB to the NP) and choosing, if possi- ble, the appropriate senses of the VERB and the NP-head from among "all their W7 senses. For example, the dis ambiguation of the defi- nition of angle(3,vi, l), to fish with a hook", determines that the relation between fish and hook is use of instrument. 1 It also determines that the intended sense of fish is (vi, l)-"to at- tempt to catch fish and the intended sense of cha°~c~fi~ InAo)idag, urved prll~;t im~re-/m~inttf° ~ senses ~or intransitive fish and "4 for the noun hook. To•ether with the five senses of with (described m the next section), these yield …

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