Tree Description Grammars and Underspecified Representations

In this thesis, a new grammar formalism called (local) Tree Description Grammar (TDG) is presented that generates tree descriptions. This grammar formalism brings together some of the central ideas in the context of Tree Adjoining Grammars (TAG) on the one hand, and approaches to underspecified semantics for scope ambiguities on the other hand. First a general definition of TDGs is presented, and afterwards a restricted variant called local TDGs is proposed. Since the elements of a local TDG are tree descriptions, an extended domain of locality as in TAGs is provided by this formalism. Consequently, local TDGs can be lexicalized, and local dependencies such as filler gap dependencies can be expressed in the descriptions occurring in the grammar. The tree descriptions generated by local TDGs are such that the dominance relation (i.e. the reflexive and transitive closure of the parent relation) need not be fully specified. Therefore the generation of suitable underspecified representations for scope ambiguities is possible. The generative capacity of local TDGs is greater than the one of TAGs. Local TDGs are even more powerful than set-local multicomponent TAGs (MC-TAG). However, the generative capacity of local TDGs is restricted in such a way that only semilinear languages are generated. Therefore these languages are of constant growth, a property generally ascribed to natural languages. Local TDGs of different rank can be distinguished depending on the form of derivation steps that are possible in these grammars. This leads to a hierarchy of local TDGs. For the string languages generated by local TDGs of a certain rank, a pumping lemma is proven that allows to show that local TDGs of rank n can generate a language Li := {a1k···a1k|k ≥ 0} iff i ≤ 2n holds. In order to describe the relation between two languages, synchronous local TDGs are introduced. The synchronization with a second local TDG does not increase the generative power of the grammar in the sense that each language generated by a local TDG that is part of a synchronous pair of local TDGs, also can be generated by a single local TDG. This formalism of synchronous local TDGs is used to describe a syntax-semantics interface for a fragment of French which illustrates the derivation of underspecified representations for scope ambiguities with local TDGs

Tree description grammars and underspecified representations

In dieser Dissertation wird ein neuer Grammatikformalismus zur Erzeugung von Baumbeschreibungen entwickelt, sogenannte (lokale) Tree Description Grammars (TDG). TDGs verbinden einige der zentrale Ideen im Zusammenhang mit Tree Adjoining Grammars (TAG) mit Ansätzen zur unterspezifizierten Semantik, speziell der Behandlung von Skopusambiguitäten. Zunächst werden allgemeine TDGs definiert, und dann wird eine eingeschränkte Variante, lokale TDGs eingeführt. Da die Elemente der Grammatik Baumbeschreibungen sind, erlaubt der Formalismus, genau wie TAG, größere lokale Bereiche. In den von (lokalen) TDGs generierten Baumbeschreibungen muss die Dominanz zwischen den Knoten (reflexive transitive Hülle der Mutter-Tochter Beziehung) nicht vollständig beschrieben sein. Dies ermöglicht die Ableitung geeigneter unterspezifizierte Repräsentationen für Skopusambiguitäten. Lokale TDGs sind mächtiger als TAGs, sogar mächtiger als mengen-lokale Multicomponent TAGs. Allerdings erzeugen lokale TDGs nur semilineare Sprachen, also Sprachen mit konstantem Kettenwachstum, eine Eigenschaft, die für natürliche Sprachen i.a. angenommen wird. Abhängig von der Form der möglichen Ableitungsschritte werden lokale TDGs verschiedenen Rangs unterschieden. Es ergibt sich eine Hierarchie, für deren einzelne Klassen ein Iterationslemma gezeigt wird. Um die Beziehung zwischen zwei Sprachen zu beschreiben, werden synchrone lokale TDGs eingeführt. Die Synchronisation mit einer zweiten lokalen TDG beeinflusst nicht die Ausdrucksstärke der Grammatik. Als Anwendungsbeispiel werden synchrone lokale TDGs zur Beschreibung einer Syntax-Semantik Schnittstelle für ein Fragment des Französischen eingesetzt. An diesem Beispiel wird die Ableitung von unterspezifizierten Repräsentationen für Skopusambiguitäten illustriert. Es zeigt sich, dass sich in dieser Architektur Inselbeschränkungen für Quantorenskopus als natürliche Folge der Lokalität der Grammatiken ergebenIn this thesis, a new grammar formalism called (local) Tree Description Grammar (TDG) is presented that generates tree descriptions. This formalism brings together some of the central ideas in the context of Tree Adjoining Grammars (TAG) on the one hand, and approaches to underspecified semantics for scope ambiguities on the other hand. First a general definition of TDGs is presented, and then a restricted variant called local TDGs is proposed. Since the elements of local TDGs are tree descriptions, an extended domain of locality as in TAGs is provided by this formalism. The tree descriptions generated by local TDGs are such that the dominance relation between nodes (reflexive transitive closure of the parent relation) need not be fully specified. This allows the generation of suitable underspecified representations for scope ambiguities. Local TDGs are more powerful than TAGs and even more powerful than set-local multicomponent TAGs. However, local TDGs generate only semilinear languages, i.e. languages of constant growth, a property generally ascribed to natural languages. Local TDGs of different rank can be distinguished depending on the derivation steps possible in these grammars. This leads to a hierarchy of local TDGs. For the classes of this hierarchy, a pumping lemma is proven. In order to describe the relation between two languages, synchronous local TDGs are introduced. The synchronization with a second local TDG does not increase the generative power of the grammar, i.e. a language generated by a local TDG that is part of a synchronous pair of local TDGs, also can be generated by a single local TDG. This formalism of synchronous local TDGs is used to describe a syntax-semantics interface for a fragment of French which illustrates the derivation of underspecified representations for scope ambiguities. In this framework, island constraints for quantifier scope ambiguities arise as a natural consequence of the localit

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

XMG : eXtensible MetaGrammar

International audienceIn this article, we introduce eXtensible MetaGrammar (xmg), a framework for specifying tree-based grammars such as Feature-Based Lexicalised Tree-Adjoining Grammars (FB-LTAG) and Interaction Grammars (IG). We argue that xmg displays three features which facilitate both grammar writing and a fast prototyping of tree-based grammars. Firstly, \xmg\ is fully declarative. For instance, it permits a declarative treatment of diathesis that markedly departs from the procedural lexical rules often used to specify tree-based grammars. Secondly, the \xmg\ language has a high notational expressivity in that it supports multiple linguistic dimensions, inheritance and a sophisticated treatment of identifiers. Thirdly, xmg is extensible in that its computational architecture facilitates the extension to other linguistic formalisms. We explain how this architecture naturally supports the design of three linguistic formalisms namely, FB-LTAG, IG, and Multi-Component Tree-Adjoining Grammar (MC-TAG). We further show how it permits a straightforward integration of additional mechanisms such as linguistic and formal principles. To further illustrate the declarativity, notational expressivity and extensibility of \xmg , we describe the methodology used to specify an FB-LTAG for French augmented with a unification-based compositional semantics. This illustrates both how xmg facilitates the modelling of the tree fragment hierarchies required to specify tree-based grammars and of a syntax/semantics interface between semantic representations and syntactic trees. Finally, we briefly report on several grammars for French, English and German that were implemented using \xmg\ and compare \xmg\ to other existing grammar specification frameworks for tree-based grammars