2,650 research outputs found
Feature Unification in TAG Derivation Trees
The derivation trees of a tree adjoining grammar provide a first insight into
the sentence semantics, and are thus prime targets for generation systems. We
define a formalism, feature-based regular tree grammars, and a translation from
feature based tree adjoining grammars into this new formalism. The translation
preserves the derivation structures of the original grammar, and accounts for
feature unification.Comment: 12 pages, 4 figures In TAG+9, Ninth International Workshop on Tree
Adjoining Grammars and Related Formalisms, 200
Feature Structures Based Tree Adjoining Grammars
We have embedded Tree Adjoining Grammars (TAG) in a feature structure based unification system. The resulting system, Feature Structure based Tree Adjoining Grammars (FTAG), captures the principle of factoring dependencies and recursion, fundamental to TAG\u27s. We show that FTAG has an enhanced descriptive capacity compared to TAG formalism. We consider some restricted versions of this system and some possible linguistic stipulations that can be made. We briefly describe a calculus to represent the structures used by this system, extending on the work of Rounds, and Kasper [Rounds et al. 1986, Kasper et al. 1986)involving the logical formulation of feature structures
Unification-Based Tree Adjoining Grammars
Many current grammar formalisms used in computational linguistics take a unification-based approach that use structures (called feature structures) containing sets of feature-value pairs. In this paper, we describe a unification-based approach to Tree Adjoining Grammars (TAG). The resulting formalism (UTAG) retains the principle of factoring dependencies and recursion that is fundamental to TAGs. We also extend the definition of UTAG to include the lexicalized approach to TAGs (see [Schabes et al., 1988]). We give some linguistic examples using UTAG and informally discuss the descriptive capacity of UTAG, comparing it with other unificationbased formalisms. Finally, based on the linguistic theory underlying TAGs, we propose some stipulations that can be placed on UTAG grammars. In particular, we stipulate that the feature structures associated with the nodes in an elementary tree are bounded ( there is an analogous stipulation in GPSG). Grammars that satisfy these stipulations are equivalent to TAG. Thus, even with these stipulations, UTAGs have more power than CFG-based unification grammars with the same stipulations
Realization of tree adjoining grammars with unification
The syntactic generator of the WIP system is based on the representation formalism "Tree Adjoining Grammars" (TAGs). We have extended the formalism by associating elementary rules of the grammar (trees) with feature structures, leading to "Tree Adjoining Grammars with Unification" (UTAGs). The extended formalism facilitates a compact and adequate representation of complex syntactic features. The contradiction between the monotonic operation of unification and the combination operation for trees - adjunction - that is nonmonotonic in a way can be solved by several approaches to realization. Two of them are presented in this work and compared with respect to the restrictions that are given by the system, i.e., the adequacy of the realization for incremental and parallel generation. It can be shown that UTAGs are subsumed by FTAGs (Feature Structure based TAGs) that have been defined by Vijay-Shanker and Joshi. That is why the results for realization can be applied to both UTAGs and a restricted version of FTAGs
Lexicalization and Grammar Development
In this paper we present a fully lexicalized grammar formalism as a
particularly attractive framework for the specification of natural language
grammars. We discuss in detail Feature-based, Lexicalized Tree Adjoining
Grammars (FB-LTAGs), a representative of the class of lexicalized grammars. We
illustrate the advantages of lexicalized grammars in various contexts of
natural language processing, ranging from wide-coverage grammar development to
parsing and machine translation. We also present a method for compact and
efficient representation of lexicalized trees.Comment: ps file. English w/ German abstract. 10 page
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 système 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 système à différents formalismes grammaticaux cibles, ouvrant ainsi la voie au multi-formalisme
Korean to English Translation Using Synchronous TAGs
It is often argued that accurate machine translation requires reference to
contextual knowledge for the correct treatment of linguistic phenomena such as
dropped arguments and accurate lexical selection. One of the historical
arguments in favor of the interlingua approach has been that, since it revolves
around a deep semantic representation, it is better able to handle the types of
linguistic phenomena that are seen as requiring a knowledge-based approach. In
this paper we present an alternative approach, exemplified by a prototype
system for machine translation of English and Korean which is implemented in
Synchronous TAGs. This approach is essentially transfer based, and uses
semantic feature unification for accurate lexical selection of polysemous
verbs. The same semantic features, when combined with a discourse model which
stores previously mentioned entities, can also be used for the recovery of
topicalized arguments. In this paper we concentrate on the translation of
Korean to English.Comment: ps file. 8 page
D-Tree Grammars
DTG are designed to share some of the advantages of TAG while overcoming some
of its limitations. DTG involve two composition operations called subsertion
and sister-adjunction. The most distinctive feature of DTG is that, unlike TAG,
there is complete uniformity in the way that the two DTG operations relate
lexical items: subsertion always corresponds to complementation and
sister-adjunction to modification. Furthermore, DTG, unlike TAG, can provide a
uniform analysis for em wh-movement in English and Kashmiri, despite the fact
that the em wh element in Kashmiri appears in sentence-second position, and not
sentence-initial position as in English.Comment: Latex source, needs aclap.sty, 8 pages, to appear in ACL-9
A Lexicalized Tree-Adjoining Grammar for Vietnamese
In this paper, we present the first sizable grammar built for Vietnamese using LTAG, developed over the past two years, named vnLTAG. This grammar aims at modelling written language and is general enough to be both application- and domain-independent. It can be used for the morpho-syntactic tagging and syntactic parsing of Vietnamese texts, as well as text generation. We then present a robust parsing scheme using vnLTAG and a parser for the grammar. We finish with an evaluation using a test suite
TuLiPA : towards a multi-formalism parsing environment for grammar engineering
In this paper, we present an open-source parsing environment (TĂĽbingen Linguistic Parsing Architecture, TuLiPA) which uses Range Concatenation Grammar (RCG) as a pivot formalism, thus opening the way to the parsing of several mildly context-sensitive formalisms. This environment currently supports tree-based grammars (namely Tree-Adjoining Grammars (TAG) and Multi-Component Tree-Adjoining Grammars with Tree Tuples (TT-MCTAG)) and allows computation not only of syntactic structures, but also of the corresponding semantic representations. It is used for the development of a tree-based grammar for German
- …