D-Tree substitution grammars

There is considerable interest among computational linguists in lexicalized grammatical frame-works; lexicalized tree adjoining grammar (LTAG) is one widely studied example. In this paper, we investigate how derivations in LTAG can be viewed not as manipulations of trees but as manipulations of tree descriptions. Changing the way the lexicalized formalism is viewed raises questions as to the desirability of certain aspects of the formalism. We present a new formalism, d-tree substitution grammar (DSG). Derivations in DSG involve the composition of d-trees, special kinds of tree descriptions. Trees are read off from derived d-trees. We show how the DSG formalism, which is designed to inherit many of the characterestics of LTAG, can be used to express a variety of linguistic analyses not available in LTAG

Exploring the underspecified world of lexicalized tree adjoining grammars

This paper presents a precise characterization of the underspecification found in Lexicalized Tree Adjoining Grammars, and shows that, in a sense, the same degree of underspecification is found in Lexicalized D-Tree Substitution Grammars. Rather than describing directly the nature of the elementary objects of the grammar, we achieve our objective by formalizing the way in which underspecification in the derived objects is interpreted: i.e., how trees are read off from derived tree descriptions. Valid tree descriptions for ltag turn out to be those that have a single acceptable interpretation, whereas those for ldsg may have multiple interpretations. In other respects, there is no difference in the way in which ltag and ldsg tree descriptions are interpreted

Tree-local MCTAG with shared nodes : an analysis of word order variation in German and Korean

Tree Adjoining Grammars (TAG) are known not to be powerful enough to deal with scrambling in free word order languages. The TAG-variants proposed so far in order to account for scrambling are not entirely satisfying. Therefore, an alternative extension of TAG is introduced based on the notion of node sharing. Considering data from German and Korean, it is shown that this TAG-extension can adequately analyse scrambling data, also in combination with extraposition and topicalization.Les Grammaires dArbres Adjoints (TAG) sont connues pour ne pas etre assez puissantes pour traiter le brouillage darguments dans des langues à ordre desmots libre. Les variantes TAG proposées jusqu´à maintenant pour expliquer le brouillage ne sont pas entièrement satisfaisantes. Nous présentons ici une extension alternative de TAG, basée sur la notion du partage de noeuds. En considerant des données de lallemand et du coréen, on montre que cette extension de TAG peut en juste proportion analyser des données de brouillage d’arguments, également en combinaison avec lextraposition et la topicalisation

Factorizing complementation in a TT-MCTAG for German

TT-MCTAG lets one abstract away from the relative order of co-complements in the final derived tree, which is more appropriate than classic TAG when dealing with flexible word order in German. In this paper, we present the analyses for sentential complements, i.e., wh-extraction, thatcomplementation and bridging, and we work out the crucial differences between these and respective accounts in XTAG (for English) and V-TAG (for German)

Interaction Grammars

Interaction Grammar (IG) is a grammatical formalism based on the notion of polarity. Polarities express the resource sensitivity of natural languages by modelling the distinction between saturated and unsaturated syntactic structures. Syntactic composition is represented as a chemical reaction guided by the saturation of polarities. It is expressed in a model-theoretic framework where grammars are constraint systems using the notion of tree description and parsing appears as a process of building tree description models satisfying criteria of saturation and minimality

Lexicalized non-local MCTAG with dominance links is NP-complete

An NP-hardness proof for non-local Multicomponent Tree Adjoining Grammar (MCTAG) by Rambow and Satta (1st International Workshop on Tree Adjoining Grammers 1992), based on Dahlhaus and Warmuth (in J Comput Syst Sci 33:456–472, 1986), is extended to some linguistically relevant restrictions of that formalism. It is found that there are NP-hard grammars among non-local MCTAGs even if any or all of the following restrictions are imposed: (i) lexicalization: every tree in the grammar contains a terminal; (ii) dominance links: every tree set contains at most two trees, and in every such tree set, there is a link between the foot node of one tree and the root node of the other tree, indicating that the former node must dominate the latter in the derived tree. This is the version of MCTAG proposed in Becker et al. (Proceedings of the 5th conference of the European chapter of the Association for Computational Linguistics 1991) to account for German long-distance scrambling. This result restricts the field of possible candidates for an extension of Tree Adjoining Grammar that would be both mildly context-sensitive and linguistically adequate

Grammaires phrastiques et discursives fondées sur les TAG : une approche de D-STAG avec les ACG

International audienceThis article presents a method to interface a sentential grammar and a discourse grammar without resorting to an intermediate processing step. The method is general enough to build discourse structures that are direct acyclic graphs (DAG) and not only trees. Our analysis is based on Discourse Synchronous TAG (D-STAG), a Tree-Adjoining Grammar (TAG)-based approach to discourse. We also use an encoding of TAG into Abstract Categorial Grammar (ACG). This encoding allows us to express a higher-order semantic interpretation that enables building DAG discourse structures on the one hand, and to smoothly integrate the sentential and the discourse grammar thanks to the modular capability of ACG. All the examples of the article have been implemented and may be run and tested with the appropriate software.Nous présentons une méthode pour articuler grammaire de phrase et grammaire de discours qui évite de recourir à une étape de traitement intermédiaire. Cette méthode est suffisamment générale pour construire des structures discursives qui ne soient pas des arbres mais des graphes orientés acycliques (DAG). Notre analyse s'appuie sur une approche de l'analyse discursive, Discourse Synchronous TAG (D-STAG), qui utilise les Grammaires d'Arbres Adjoint (TAG). Nous utilisons pour ce faire un encodage des TAG dans les Grammaires Catégorielles Abstraites (ACG). Cet encodage permet d'une part d'utiliser l'ordre supérieur pour l'interprétation sémantique afin de construire des structures qui soient des DAG et non des arbres, et d'autre part d'utiliser les propriétés de composition d'ACG pour réaliser naturellement l'interface entre grammaire phrastique et grammaire discursive. Tous les exemples proposés pour illustrer la méthode ont été implantés et peuvent être testés avec le logiciel approprié

Une grammaire d'interaction du français

National audienceNous présentons une grammaire du français à relativement large couverture dans le formalisme des grammaires d'interaction. Ce formalisme combine deux idées-forces : la grammaire est vue comme un système de contraintes à travers la notion de description d'arbre, et la sensibilité aux ressources de la langue est utilisée comme principe de composition syntaxique à l'aide de la notion de polarité. Nous donnons un aperçu du pouvoir expressif du formalisme en modélisant quelques phénomènes linguistiques significatifs et nous montrons que l'architecture de la grammaire répond à un souci de réutilisabilité et de faisabilité, crucial quand on cherche à construire des ressources à large couverture : distinction entre une grammaire source modulaire et une grammaire objet obtenue par compilation de la première, indépendance du lexique par rapport à la grammaire. Enfin, nous présentons les résultats d'une évaluation de la grammaire sur une suite de phrases tests, effectuée à l'aide de l'analyseur syntaxique LEOPAR

Descriptions d'arbres avec polarités : les Grammaires d'Interaction

Colloque avec actes et comité de lecture. nationale.National audienceNous présentons un nouveau formalisme linguistique, les Grammaires d'Interaction, dont les objets syntaxiques de base sont des descriptions d'arbres, c'est-à-dire des formules logiques spécifiant partiellement des arbres syntaxiques. Dans ce contexte, l'analyse syntaxique se traduit par la construction de modèles de descriptions sous la forme d'arbres syntaxiques complètement spécifiés. L'opération de composition syntaxique qui permet cette construction pas à pas est contrôlée par un système de traits polarisés agissant comme des charges électrostatiques

Interfacing Sentential and Discourse TAG-based Grammars

International audienceTree-Adjoining Grammars (TAG) have been used both for syntactic parsing, with sentential grammars, and for discourse parsing, with discourse grammars. But the modeling of discourse connectives (coordinate conjunctions, subordinate conjunctions , adverbs.. .) in TAG-based formalisms for discourse differ from their modeling in sentential grammars. Because of this mismatch, an intermediate, not TAG-related, processing step is required between the sentential and the discourse processes, both in parsing and in generation. We present a method to smoothly interface sentential and discourse TAG grammars, without using such an intermediate processing step. This method is based on Abstract Categorial Grammars (ACG) and relies on the modularity of the latter. It also provides the possibility, as in D-STAG, to build discourse structures that are direct acyclic graphs (DAG) and not only trees. All the examples may be run and tested with the appropriate software