The Correct Place of Lexical Semantics in Interlingual MT

1. lntroducti(m Inlerlingual MT has tyl)ically come to incltLde a syntactic analysis of source language (SI ,) text followed hy its semm~tic interpretation ~.uld representation in terms of a text meaning representation (TMR) scheme, an interlin-gu,'t. Recently two distinct views of the nattzre of lhe inlerlingua have become current-one based on a worhl model (e.g., Nirenburg et al., 1992) and another one based on the notion of lexieal conceptual structure (LCS) (e.g., Dorr, 1992). In this paper we analyze the role of LCS in the extraction of text memfing and argue that, thotlgh it cannot be considered an interlingua when used by itself, it etmtribtltes signilic+mtly 1o the Sl)eciiication of an ac~ teal interlingua. The task of ;el interlingual MT system btfilder is, then, to lind tt way to integrate the informalion provided in LCS into an ontology-molivaled text meaning representation serving as interlingua. In this paper, we propose a model for Ibis integration mid illustrate the processes and static knowledge sources involved, centrally including tile lexicon. In Section 2 wc propose a model of MT that involves both an LCS-based lexical semantic slruclure and a 'FMR that is not b:tsed on LCS. Because our lexicon lbrmal-ism does not represent LeSs, but semantic role names that serve ~us labels for LCS variables, we will use Ihe abhreviation SDI+S (for synlax-driven lexical semanlies, Nirenburg grad Levin, 1992) in reference 1o our system instead of LCS. We argue that TMR and SI)LS are both necessary and that they are distinct. This model forms the basis of lexical-semanlic treatment of lexls in the multilingual MTl)rojectMikrokosmos. In Seclion 3 we present specific exmnples as analyzed in Mikrokosmos. Wc illustrate the static knowledge sources (primarily the lexicon) and the representations that are l)roduccd (syntax, lexical semantics, and TMR). The Mikrokosmos model is based on a Iheory of form-to-meaning corrcsl)ondence which relies on the concept of a society of microlheories inle-grated in a noLi-Slratiticational manner. We brielly sketch the main points of this theory in the [inal SeCliOn of this paper, 2. The model Traditionally, intcrlingual MT systems which employ a full-Iflown syntactic module (e.g., KBMT-g9 (Goodman • ~tnd Nircifl)mg, 1992) or KANT (Carl~onell et al., 1992)) use a single mapping between syntactic structure and in-lerlingua. In Mikrokosmos, we propose a different model, as illustrated in Figure 1. Lexical-cotlcel~lual SlrUCtures (LCSs) have been suggested its meaning represenlalions for n,'ilural language sentences produced in accordance with the …