150 research outputs found
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 Ă ordre desmots libre. Les variantes TAG proposĂ©es jusquÂŽĂ maintenant pour expliquer le brouillage ne sont pas entiĂšrement satisfaisantes. Nous prĂ©sentons ici une extension alternative de TAG, basĂ©e sur la notion du partage de noeuds. En considerant des donnĂ©es de lallemand et du corĂ©en, on montre que cette extension de TAG peut en juste proportion analyser des donnĂ©es de brouillage dâarguments, Ă©galement en combinaison avec lextraposition et la topicalisation
A descriptive characterization of multicomponent tree adjoining grammars
Multicomponent Tree Adjoining Grammars (MCTAG) is a formalism that has been shown to be useful for many natural language applications. The definition of MCTAG however is problematic since it refers to the process of the derivation itself: a simultaneity constraint must be respected concerning the way the members of the elementary tree sets are added. Looking only at the result of a derivation (i.e., the derived tree and the derivation tree), this simultaneity is no longer visible and therefore cannot be checked. I.e., this way of characterizing MCTAG does not allow to abstract away from the concrete order of derivation. Therefore, in this paper, we propose an alternative definition of MCTAG that characterizes the trees in the tree language of an MCTAG via the properties of the derivation trees the MCTAG licences.Il a Ă©tĂ© montrĂ© que les Grammaires dArbres Adjoints Ensemblistes (Multicomponent Tree Adjoining Grammars, MCTAG) sont trĂšs utiles pour des applications TAL. Pourtant, la dĂ©finition des MCTAG est problĂ©matique parce quelle fait rĂ©fĂ©rence au procĂšs de dĂ©rivation mĂȘme : une contrainte de simultanĂ©itĂ© est imposĂ©e concernant la façon dont on ajoute les membres dun mĂȘme ensemble darbres. En regardant uniquement le rĂ©sultat dâune dĂ©rivation, cest-Ă -dire larbre dĂ©rivĂ© et larbre de dĂ©rivation, cette simultanĂ©itĂ© nest plus visible. Par consĂ©quent pour vĂ©rifier la contrainte de simultanĂ©itĂ©, il faut toujours considĂ©rer lordre concret des pas de la dĂ©rivation. Afin dĂ©viter cela, nous proposons une caractĂ©risation alternative de MCTAG qui permet une abstraction de lordre de dĂ©rivation : Les arbres gĂ©nĂ©rĂ©s par la grammaire sont caractĂ©risĂ©s par les propriĂ©tĂ©s de leurs arbres de dĂ©rivation
A declarative characterization of different types of multicomponent tree adjoining grammars
Multicomponent Tree Adjoining Grammars (MCTAGs) are a formalism that has been shown to be useful for many natural language applications. The definition of non-local MCTAG however is problematic since it refers to the process of the derivation itself: a simultaneity constraint must be respected concerning the way the members of the elementary tree sets are added. Looking only at the result of a derivation (i.e., the derived tree and the derivation tree), this simultaneity is no longer visible and therefore cannot be checked. I.e., this way of characterizing MCTAG does not allow to abstract away from the concrete order of derivation. In this paper, we propose an alternative definition of MCTAG that characterizes the trees in the tree language of an MCTAG via the properties of the derivation trees (in the underlying TAG) the MCTAG licences. We provide similar characterizations for various types of MCTAG. These characterizations give a better understanding of the formalisms, they allow a more systematic comparison of different types of MCTAG, and, furthermore, they can be exploited for parsing
A declarative characterization of different types of multicomponent tree adjoining grammars
Multicomponent Tree Adjoining Grammars (MCTAG) is a formalism that has been shown to be useful for many natural language applications. The definition of MCTAG however is problematic since it refers to the process of the derivation itself: a simultaneity constraint must be respected concerning the way the members of the elementary tree sets are added. This way of characterizing MCTAG does not allow to abstract away from the concrete order of derivation. In this paper, we propose an alternative definition of MCTAG that characterizes the trees in the tree language of an MCTAG via the properties of the derivation trees (in the underlying TAG) the MCTAG licences. This definition gives a better understanding of the formalism, it allows a more systematic comparison of different types of MCTAG, and, furthermore, it can be exploited for parsing
Developing a TT-MCTAG for German with an RCG-based parser
Developing linguistic resources, in particular grammars, is known to be a complex task in itself, because of (amongst others) redundancy and consistency issues. Furthermore some languages can reveal themselves hard to describe because of specific characteristics, e.g. the free word order in German. In this context, we present (i) a framework allowing to describe tree-based grammars, and (ii) an actual fragment of a core multicomponent tree-adjoining grammar with tree tuples (TT-MCTAG) for German developed using this framework. This framework combines a metagrammar compiler and a parser based on range concatenation grammar (RCG) to respectively check the consistency and the correction of the grammar. The German grammar being developed within this framework already deals with a wide range of scrambling and extraction phenomena
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)
XMG : eXtending MetaGrammars to MCTAG
In this paper, we introduce an extension of the XMG system (eXtensibleMeta-Grammar) in order to allow for the description of Multi-Component Tree Adjoining Grammars. In particular, we introduce the XMG formalism and its implementation, and show how the latter makes it possible to extend the system relatively easily to different target formalisms, thus opening the way towards multi-formalism.Dans cet article, nous présentons une extension du systÚme XMG (eXtensible MetaGrammar) afin de permettre la description de grammaires darbres adjoints à composantes multiples. Nous présentons en particulier le formalisme XMG et son implantation et montrons comment celle-ci permet relativement aisément détendre le systÚme à différents formalismes grammaticaux cibles, ouvrant ainsi la voie au multi-formalisme
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 33:456â472, 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
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Complexity, Parsing, and Factorization of Tree-Local Multi-Component Tree-Adjoining Grammar
Tree-Local Multi-Component Tree-Adjoining Grammar (TL-MCTAG) is an appealing formalism for natural language representation because it arguably allows the encapsulation of the appropriate domain of locality within its elementary structures. Its multicomponent structure allows modeling of lexical items that may ultimately have elements far apart in a sentence, such as quantifiers and Wh-words. When used as the base formalism for a synchronous grammar, its flexibility allows it to express both the close relationships and the divergent structure necessary to capture the links between the syntax and semantics of a single language or the syntax of two different languages. Its limited expressivity provides constraints on movement and, we posit, may have generated additional popularity based on a misconception about its parsing complexity. Although TL-MCTAG was shown to be equivalent in expressivity to TAG when it was first introduced (Weir 1988), the complexity of TL-MCTAG is still not well-understood. This paper offers a thorough examination of the problem of TL-MCTAG recognition, showing that even highly restricted forms of TL-MCTAG are NP-complete to recognize. However, in spite of the provable difficulty of the recognition problem, we offer several algorithms that can substantially improve processing efficiency. First, we present a parsing algorithm that improves on the baseline parsing method and runs in polynomial time when both the fan-out and rank of the input grammar are bounded. Second, we offer an optimal, efficient algorithm for factorizing a grammar to produce a strongly-equivalent TL-MCTAG grammar with the rank of the grammar minimized.Engineering and Applied Science
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