Valency Theory in Stratificational MT-System

This paper tries to investigate valency theory as a linguistic tool in machine translation.There are three main areas in which major questions arise: (i) Valency theory itself. I sketch a valency theory in linguistic terms which includes the discussion of the nature of dependency representation as an interface for semantic description. (2) The dependency representation in the translation process. I try to sketch the different roles of dependency representation in analysis and generation. 3) The impl~m~_ntation of valency theory in an MTsystem. I give a few examples for how a valency d~xzription could be impleme~ted in the EUROTRAformalism. O. Introduct:[on This paper ~ies to apply a piece of established linguistics, known as valency theory, to the problem of machine translation. As such, it is meant to fit into the forthcoming EUROTRA MT system, though it does not deal with EUROTRA problems sp~;ifically. There are two aspects which play a role in the building of ~Ln Ff£-syste~; (i) the development of linguistic specifications and (2) the development of a formalism which allows for the implemenlmtion of linguistic results. ~lis paper aninly deals with the first aspect and ~/~us relates not only to EUNOTRA but also at least to all stratificational systems, i.e. systems t2mt break up the translation process into a sequence of sJx~#ler translation processes. Furthermore it relates at least to any system wi]ich uses dependency/valency inforalation as e.g. IAgG does with its functional structure. In EUROTRA, the level where information about dependency/valency is used is the hqIS (EurotraRelational-Structure) which lies between the constitueat stzncture (ECS) and the semantic intea-face stzucture (IS). So, in EOROZRA terms I try here to give a kind of ERS-definition in the language of empirical linguistics without touching the formalism itself. The investigation divides into three parts: (i) the sketch of a v~l.ency theory which comprises the following points: the informal definition of the concepts valency, cc~plement,ar~ adjunct, thereby trying to give a definition which holds for verbs, adjectives, nouns, and prepositions, the operationalizati~1 of the complement adjunct distinction derived frc~! this definition, the classification of the complements, a subclassification of f~e complement classes (Cclasses) according to their syntactic realization, and the determination of the relevant sentence patterns, a short discussion of the relation of the dependency level to constituency level and from dependency level to semantic representation. (2) the application of the linguistic specifications to the problem of MT which llas to investigate the role of dependency representation (D-representation) (oi" rather the role of the transitions to D-representation, since levels do not "play a role") in an,91ysis and generation. (3) the way the gained linguistic information can be implemented according to the EOROTRA formalism. i. Outline of a Syntactic Val~ ~_~ I. 1 Definition of Concej3~s The syntactic vale~zy of an el~ent of a word class (a nonterminal category) is its property to bind a certain number and a certa~ kind of syntagma. Those valency--bound syn'l~o~,'e:-~ a re t h e oon~icm~e~ts. 'I~e s%a~tagnms which are ~t valency-bound are the adjuncts. All syntagmas which are obligatory in a syntactical sense are valency-bound, i.e. the sentence a~st contain tt~t item otherwise it would not be complete. Bedsides the obligatory syntagmas the wordL~ubclass specific elea~ts are valency-bound (Engel 1982). Wordsubclass specific e]em~--nts are those syntagmas which can occur only with elemlents of wordsubclasses. i. 2 Qperationalization of valency 'fhis point usually forms the major part of each paper on vale~cy theory and mostly consists of a discussion of various proposed tests in the literature on valency theory showing their deficiencies and ccmdng up with a new proposal.