The thesis describes novel techniques and algorithms for the practical parsing of realistic Natural Language (NL) texts with a wide-coverage unification-based grammar of English. The thesis tackles two of the major problems in this area: firstly, the fact that parsing realistic inputs with such grammars can be computationally very expensive, and secondly, the observation that many analyses are often assigned to an input, only one of which usually forms the basis of the correct interpretation. The thesis starts by presenting a new unification algorithm, justifies why it is well-suited to practical NL parsing, and describes a bottom-up active chart parser which employs this unification algorithm together with several other novel processing and optimisation techniques. Empirical results demonstrate that an implementation of this parser has significantly better practical

We present an implementation of a chart-based head-corner parsing algorithm for lexicalized Tree Adjoining Grammars. We report on some practical experiments where we parse 2250 sentences from the Wall Street Journal using this parser. In these experiments the parser is run without any statistical pruning; it produces all valid parses for each sentence in the form of a shared derivation forest. The parser uses a large Treebank Grammar with 6789 tree templates with about 120; 000 lexicalized trees. The results suggest that the observed complexity of parsing for LTAG is dominated by factors other than sentence length.

We study parsing of tree adjoining grammars with particular emphasis on the use of shared forests to represent all the parse trees deriving a well-formed string. We show that there are two distinct ways of representing the parse forest one of which involves the use of linear indexed grammars and the other the use of context-free grammars.

Recent work has shown how basic ideas of the minimalist tradition intransformational syntax can be captured in a simple generative formalism, a"der:"AII] al minimalism." Thisfr]]I[L" can model "rel nant movement" analyses, which yield mor e complex antecedent-tr ace r elations, suggesting a new and significant sense in which linguistic str ctur esar "chain based." Michaelis (1998) showed that these grI] mar cor" spond to a certain kind of linear context free r write system, and this paper takes the next step of adapting ther ecognition methods for "non-concatenative"grOO[]" (Weir 1988; Seki et al., 1991; Boullier , 1999). This tur ns out to be quite straightforward once the grammars are set out appropriately.

: In this paper we present a new parsing algorithm for linear indexed grammars (LIGs) in the same spirit as the one described in (Vijay-Shanker and Weir, 1993) for tree adjoining grammars. For a LIG L and an input string x of length n, we build a non ambiguous context-free grammar whose sentences are all (and exclusively) valid derivation sequences in L which lead to x. We show that this grammar can be built in O(n 6 ) time and that individual parses can be extracted in linear time with the size of the extracted parse tree. Though this O(n 6 ) upper bound does not improve over previous results, the average case behaves much better. Moreover, practical parsing times can be decreased by some statically performed computations. Key-words: mildly context-sensitive parsing, ambiguity, parse tree, shared parse forest. (R#sum# : tsvp) This report is an extended version of the ACL'96 paper (Boullier, 1996). * E-mail: Pierre.Boullier@inria.fr Unit de recherche INRIA Rocquencourt Domaine de ...

Introduction In (Boullier 98), we presented range concatenation grammars (RCGs), a syntactic formalism which is a variant of literal movement grammars (LMGs), described in (Groenink 97), and which is also related to the framework of LFP developed by (Rounds 88). In fact it may be considered to lie halfway between their respective string and integer versions; RCGs retain from the string version of LMGs or LFPs the notion of concatenation, applying it to ranges rather than strings, and from their integer version the ability to handle only (part of) the source text. The basis of RCGs is the notion of range, a couple of integers hi :: ji which denotes the occurrence of some substring a i+1 : : : a j in an input string a 1 : : : a n . Of course, only consecutive ranges can be concatenated into a new range . This formalism, which extends CFGs, aims at being a convincing challenger as a syntactic base for various tasks, especially in natural language processing. We have shown that the po

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We extend a recently proposed algorithm for n-best unpacking of parse forests to deal efficiently with (a) Maximum Entropy (ME) parse selection models containing important classes of non-local features, and (b) forests produced by unification grammars containing significant proportions of globally inconsistent analyses. The new algorithm empirically exhibits a linear relationship between processing time and the number of analyses unpacked at all degrees of ME feature nonlocality; in addition, compared with agendadriven best-first parsing and exhaustive parsing with post-hoc parse selection it leads to improved parsing speed, coverage, and accuracy.

This ESSLLI workshop is devoted to connecting the linguistic use of resource logics and categorial grammar to minimalist grammars and related generative grammars. Minimalist grammars are relatively recent, and although they stem from a long tradition of work in transformational grammar, they are largely informal apart from a few research papers. The study of resource logics, on the other hand, is formal and stems naturally from a long logical tradition. So although there appear to be promising connections between these traditions, there is at this point a rather thin intersection between them. The papers in this workshop are consequently rather diverse, some addressing general similarities between the two traditions, and others concentrating on a thorough study of a particular point. Nevertheless they succeed in convincing us of the continuing interest of studying and developing the relationship between the minimalist program and resource logics. This introduction reviews some of the basic issues and prior literature. 1 The interest of a convergence What would be the interest of a convergence between resource logical investigations of

In this paper we will describe a polynomial time Earley-style predictive parser for D-Tree Grammars (DTG). DTG were designed to share some of the advantages of TAG while overcoming some of its limitations. In developing parsers for TAG it has turned out to be useful to make use of a direct mapping from TAG to Linear Indexed Grammars (LIG) and to develop algorithms that work with the resulting LIG. In the case of DTG we use a similarly direct mapping into what we call Linear Prioritized Multiset Grammar (LPMG). This makes it possible to give a straightforward statement of the parsing algorithm. 1. Motivation Rambow, Vijay-Shanker and Weir (1995), we define a new grammar formalism, called D-Tree Grammars (DTG), which arises from work on Tree-Adjoining Grammars (TAG) (Joshi et al., 1975). A salient feature of TAG is the extended domain of locality it provides. Each elementary structure can be associated with a lexical item (as in Lexicalized TAG (LTAG) (Joshi and Schabes, 1991)). Propert...