Inria / Raweb 2004

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Project-Team : calligramme

Section: Application Domains

Modelling the Syntax and Semantics of Natural Languages

Abstract Categorial Grammars

Abstract Categorial Grammars (ACGs) are a new categorial formalism based on Girard's linear logic. This formalism, which sticks to the spirit of current type-logical grammars, offers the following features:

Abstract categorial grammars are not intended as yet another grammatical formalism that would compete with other established formalisms. It should rather be seen as the kernel of a grammatical framework in which other existing grammatical models may be encoded.

Interaction Grammars

Interaction Grammars (IGs) are a linguistic formalism that aims at modelling both the syntax and the semantics of natural languages according to the following principles:

The formalism of IG stems from a reformulation of proof nets of Intuitionisitc Linear Logic (which have very specific properties) in a model-theoretical framework [48] and it was at first designed for modelling the syntax of natural languages [49].

Dependency Grammars

Dependency grammar (DG) is a resource sensitive grammar formalism related to categorial grammar. An important appeal of DG is that it naturally permits non-projective analyses and is thus especially well suited for languages with free or freer word-order (e.g. Czech, German, Russian, etc...). However, free(r) word-order poses an especially thorny challenge for processing: all efficient parsing algorithms rely fundamentally on properties of adjacency and projectivity. Duchier [39] described a declarative formulation of valid DG analyses, and showed how effective model elimination using constraint programming technology could serve as a practical foundation for DG parsing.

Of course, not all languages have free(r) word-order, and even for those, word-order is not really entirely free. The next challenge for DG was to permit an account of word-order. While this had been attempted in the past, no proposal to date was especially appealing. Duchier and Debusmann [38] proposed Topological Dependency Grammar (TDG) which took inspiration in the topological field theory that is at the heart of traditional German descriptive syntax. In TDG, an analysis consists of two trees: a non-ordered ID tree of syntactic dependencies and an ordered and projective LP tree of topological dependencies. The ID tree is related to the LP tree through a process of emancipation. Thus, in TDG, macroscopic word-order phenomena are not modeled directly, rather they are seen as emerging from (1) simple lexical constraints and (2) from the mutually constraining interactions of the ID and LP trees.

Meta-grammars and lexical resources

Every lexicalized grammar formalism (tree adjoining grammar, categorial grammar, interaction grammar, dependency grammar) is faced with the problem of organizing and structuring the lexicon. On the one hand, there is the pragmatic consideration that the lexicon should be modularly organized so as to make it easier to develop, maintain and extend. On the other hand it should also be possible to express linguistic generalizations (e.g. passivisation schemata).

Marie-Hélène Candito proposed and developed a meta-grammatical approach for lexicalized TAGs (Tree Adjoining Grammars) that generated a lot of interest. Unfortunately, it also exhibited a number of infelicitous properties, in particular difficulties in managing named entities and implicit crossings.