KASSYS: A Definition Acquisition System in Natural Language

KASSYS: A DEFINITION ACQUISITION SYSTEM IN NATURAL LANGUAGE Patricc Hernert L.I.F.O., R. L. de Vinci, B.P. 6759, 45067 Orldans Ccdex 2, France E-mail: hernert @chambord.univ-orleans. fr Abstract: This paper is an introdnction to KASSYS, a system that has been designed to extract information from detining statements in natural language. Only hy- peronymous detinitions are dealt with here, for which systematic processing has been devised and itnl)lenmnted in tlte initial version of the system. The paper describes how KASSYS buiMs a taxinomie hierarchy by extracting the hyperonyms from these definitions. It also explains the way in which the system can answer closed questions (yes/no), thus enabling the user to check very quickly that a definition has been assimilated correctly. The under- lying forrnalism is that of conceptual graphs, with which the reader is assumed to be familiar. Keywords: Conceptual graphs, hyperm~ymous defini- tion, knowledge acquisition, question (yes/no). I-INTRODUCTION The mm of KASSYS, the system described here, is to acquire lexicographical definitions expressed in French, to extract from these definitions a carefully chosen concep- tual structure, to save this structure in a tile, and to then be able to use it, where appropriate, for the semantic analysis of a text or during the search for an artswer to a question put by the user. + The formalistn which has been adopted for the representation of the detinitions is that o1' concep- tual graphs, 2 that the reader is assumed to understand. All the examples will be given in the feral of statements in natural language, and the operations actually pcrfof med by the system on the conceptual stnmtut'es extracted from these statements will not be described. This paper is limited to hyperonymous delinitions. It ;list) shows, very brietly, how KASSYS can answer cet+tain types of ques- tion. 2. KNOWLIgl)GE EXTRACTION 2.1 - Some points concerning hyperonynmus detinl- lions Ilyperonymy/hyponymy can be delined its follows: term A is said to be a hyperonym of term B, or alter- natively that term B is a hyponym of term A, if the set of instances of term B is included in the set of instances of term A. This gives the following corollary: the set of se- mantic features that make ttp the elements of A is included in the set of sem,'mtic featnres that make up the elements of B; the elelnents of B are saM to inherit the sem,'mtic features that are common to the elements of A. llere wc b For a complete descriplion of the initM version of KASS YS, please refer to (llernert 93). 2Cf. (Sowa 84). have tile notion of inheritance of semantic features that is fundanmntal to tile theory of semantic netwm'ks. Ilyperonymy is thus defined by the gencral relation: (1) (A is a hyperonym of B) ~ (V x, B(x) D A(x)) The equiwflcnt in natural hmguage of (1) is: (2) (A is a hyperonyna of B) ~ (All P, is A) For example, lhe definition of the concept bee: (3) bee: a social insect which produces …

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