Discourse Semantics Meets Lexical Field Semantics

Discourse Semantics Meets Lexical Field Semantics Beate Firzlaff and Daniela S. Kunz German National Research Center for Information Technology (GMD) KONTEXT Natural Language Systems Dolivostr. 15 D-64293 Darmstadt, Germany {firzlaff, kunz}@darmstadt.gmd.de Abstract The focus of this article is the integra- tion of two different perspectives on lexi- cal semantics: Discourse Representation Theory's (DRT) inferentially motivated approach and Semantic Emphasis The- ory's (SET) lexical field based view. A new joined representation format is de- veloped which is exemplified by anal- yses of German verbs. The benefits thereof are on both sides. DI/T gains basic entries for whole lexical fields and, furtherlnore, a systematic interface be- tween semantic and syntactic argument structures. SET profits both from the much larger semantic coverage and from the fine grained lexical analyses which reflect inferential behaviour. 1 Introduction The construction of lexical entries is one of the crucial and challenging tasks given in the field of computational linguistics. In the ideal case, lexi- cal entries fulfill, among others, two requirements. First, the representations are suitably fine grained such that they capture lexeme-speeific distinc- tions. Second, the lexical entries are sufficiently general, for reflecting similarities between single lexemes. Furthermore, the information they con- tain should systematically link various levels of description, e.g. syntax and semantics as well as referential and inferential potential. The latter is of special interest for text analysis as opposed to sentence analysis (eft for example (Haenelt, 1994); (Haenelt and KSnyves-Tdth, 1991)). Corresponding to these requirements, we ex- ploit the specific strengths of two distinct seman- tic theories. These theories are Discourse Rep- resentation Theory (DRT) ((Kamp and Reyle, 1993); (FraCaS-DS, 1994)) and Semantic Empha- sis Theory (SET)((Kunze, 1991); (Kunze, 1993)). However, our central goal is an integration of D113' and SET. It will be shown that this integration is possible and of benefit to both theories as well as to the construction of lexical entries. To achieve our overall objective, the following four points will be exemplified by joined representations of Ger- man verbs: • DRT profits from SET's systematic deriva- tions of thematic roles and of morpho-syntaetic features on the basis of predicate-argument- structures. These features include both gram- matical and prepositional case. • DRT gains a purely semantically motivated ori- entation towards lexical fields. • Dll[l' covers much more semantic phenomena than SET. Therefore, DI{T offers SET the pos- sibility to test its results against a semantic background that e.g. includes plurals, tenses, and attitudes. • DRT's fine grained lexical analyses are grounded in inferential behaviour. These lex- ical distinctions mark possible starting points for refining SET's representations. The paper is structured as follows: DRT's and SET's basic motivations, principles and formal means concerning lexical semantics are retraced ~n sections 2 and 3. The new joined representation format is introduced in section 4 by analysing the German verbs leihen (in its variant to lend) and verschenken (in its variant to give as a present). Moreover, section 4 provides evidence that the four main points stated above are backed up by the …

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