Topic
Tree-adjoining grammar
About: Tree-adjoining grammar is a research topic. Over the lifetime, 2491 publications have been published within this topic receiving 57813 citations.
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TL;DR: An efficient algorithm is proposed to solve one of the problems associated to the use of weighted and stochastic Context-Free Grammars: the problem of computing the N best parse trees of a given string.
Abstract: Context-Free Grammars are the object of increasing interest in the pattern recognition research community in an attempt to overcome the limited modeling capabilities of the simpler regular grammars, and have application in a variety of fields such as language modeling, speech recognition, optical character recognition, computational biology, etc.
This paper proposes an efficient algorithm to solve one of the problems associated to the use of weighted and stochastic Context-Free Grammars: the problem of computing the N best parse trees of a given string. After the best parse tree has been computed using the CYK algorithm, a large number of alternative parse trees are obtained, in order by weight (or probability), in a small fraction of the time required by the CYK algorithm to find the best parse tree. This is confirmed by experimental results using grammars from two different domains: a chromosome grammar, and a grammar modeling natural language sentences from the Wall Street Journal corpus.
40 citations
31 Mar 1992
TL;DR: The use of Common Lisp without its object language addition and the use of the X Window interface to Common Lisp (CLX) for the implementation of XTAG, a development of tree-adjoining grammars and their parsers, are described.
Abstract: We describe a workbench (XTAG) for the development of tree-adjoining grammars and their parsers, and discuss some issues that arise in the design of the graphical interface.Contrary to string rewriting grammars generating trees, the elementary objects manipulated by a tree-adjoining grammar are extended trees (i.e. trees of depth one or more) which capture syntactic information of lexical items. The unique characteristics of tree-adjoining grammars, its elementary objects found in the lexicon (extended trees) and the derivational history of derived trees (also a tree), require a specially crafted interface in which the perspective has shifted from a string-based to a tree-based system. XTAG provides such a graphical interface in which the elementary objects are trees (or tree sets) and not symbols (or strings).The kernel of XTAG is a predictive left to right parser for unification-based tree-adjoining grammar [Schabes, 1991]. XTAG includes a graphical editor for trees, a graphical tree printer, utilities for manipulating and displaying feature structures for unification-based tree-adjoining grammar, facilities for keeping track of the derivational history of TAG trees combined with adjoining and substitution, a parser for unification based tree-adjoining grammars, utilities for defining grammars and lexicons for tree-adjoining grammars, a morphological recognizer for English (75 000 stems deriving 280 000 inflected forms) and a tree-adjoining grammar for English that covers a large range of linguistic phenomena.Considerations of portability, efficiency, homogeneity and ease of maintenance, lead us to the use of Common Lisp without its object language addition and to the use of the X Window interface to Common Lisp (CLX) for the implementation of XTAG.XTAG without the large morphological and syntactic lexicons is public domain software. The large morphological and syntactic lexicons can be obtained through an agreement with ACL's Data Collection Initiative.XTAG runs under Common Lisp and X Window (CLX).
40 citations
21 Aug 1989
TL;DR: This paper shows some close relationships between context-free graph grammars and concepts from string language theory and tree language theory, and shows how the generated graph languages can be described in terms of regular tree languages and regular string languages.
Abstract: The aim of this paper is to show some close relationships between context-free graph grammars and concepts from string language theory and tree language theory. There are many kinds of context-free graph grammars (see, e.g., [EhrNagRozRos]). Some are node rewriting and others are edge rewriting. In both cases a production of the grammar is of the form X ~ (D,B). Application of such a production to a labeled graph H consists of removing a node (or edge) labeled X from H, replacing it by the graph D, and connecting D to the remainder of H according to the embedding procedure B. Since these grammars are context-free in the sense that one node (or edge) is replaced, their derivations can be modeled by derivation trees, as in the case of strings. However, the grammar may still be context-sensitive in the sense that the (edges of the) graph generated according to the derivation tree may depend on the order in which the productions are applied. A graph grammar that does not suffer from this context-sensitivity is said to be confluent (or to have the finite Church-Rosser property), see [Cou] for a uniform treatment. Thus, for a confluent graph grammar G, each derivation tree of G yields a unique graph in the graph language generated by G. Due to this close relationship to (derivation) trees, the generated graph languages can be described in terms of regular tree languages and regular string languages. We will show this for the particular case of the (node rewriting) edNCE graph grammars, studied in [Kau, Bral/2, EngLeiRozl/2, Sch, EngLeiWel, EngLeil/2, EngRoz] (and called DNELC grammars in [Bra2]).
39 citations
01 Aug 1998
TL;DR: It is shown that using descriptions to describe the semantic representation of discourse permits a monotone treatment of local ambiguity; a deterministic treatment of global ambiguity; and a distinction to be made between “simple” local ambiguity and “garden-path’ local ambiguity.
Abstract: Descriptions In recent years, both formal and computational linguistics have been exploiting descriptions of structures where previously the structures themselves were used The practice started with (Marcus et al, 1983), who demonstrated the value of (syntactic) tree descriptions for near-deterministic incremental parsing Vijay-Shankar (Vijay-Shankar and Joshi, 1988; Vijay-Shankar, 1992) used descriptions to maintain the monotonicity of syntactic derivations in the framework of Feature-Based Tree Adjoining Grammar In semantics, both (Muskens, 1997) and (Egg et al, 1997) have shown the value of descriptions as an underspecified representation of scope ambiguities The current paper further extends the use of descriptions, from individual sentences to discourse, showing their benefit for incremental, near-deterministic discourse processing In particular, we show that using descriptions to describe the semantic representation of discourse permits: (1) a monotone treatment of local ambiguity; (2) a deterministic treatment of global ambiguity; and (3) a distinction to be made between “simple” local ambiguity and “garden-path” local ambiguity
39 citations
04 Oct 1994
TL;DR: A class of relation grammars that satisfy the context-freeness property is defined, which is an essential condition to solve the membership problem in polynomial time, and a predictive parsing algorithm is designed for such Grammars.
Abstract: We define a class of relation grammars that satisfy the context-freeness property, which is an essential condition to solve the membership problem in polynomial time. The context-freeness property is used to design a predictive parsing algorithm for such grammars. The algorithm has a polynomial time behaviour when applied to grammars which generate languages having the additional properties of connections and degree-boundedness. One remarkable result is that a polynomial time complexity is obtained without imposing (total or partial) ordering on the symbols of input sentences. >
39 citations