This thesis proposes a strongly lexicalist approach to machine translation and applies it to the translation of spatial prepositions and prepositional expressions between English and Spanish. Bilingual contrastive knowledge resides solely in the bilingual lexicon and is structured in the form of correspondences between sets of source and target language lexemes related through indices. The resulting architecture maximizes the independence of the monolingual and bilingual components. This independence is demonstrated by developing a grammar of Spanish which is significantly different in its constructions from its analogous English grammar. In particular, relative clauses are analysed through a single rule that allows gaps in subject position, while clitic climbing and doubling are handled through mechanisms not normally found in grammatical descriptions of English. Bilingual lexical rules, in conjunction with the bilingual lexicon, constitute a single, motivated and well defined mechani...

Abstract. Context unification (CU) is the open problem of solving context equations for trees. We distinguish a new decidable variant of CU– well-nested CU – and present a new unification algorithm that solves well-nested context equations in non-deterministic polynomial time. We show that minimal well-nested solutions of context equations can be composed from the material present in the equation (see Theorem 1). This property is wishful when modeling natural language ellipsis in CU. 1

In this paper, we argue that both modals and tense expressions are anaphoric, and can be handled by the same discourse mechanisms underlying the resolution of pronouns and other anaphoric devices. In support of this, we show that both modals and tense give rise to sloppy identity patterns. We explain this by assuming all anaphors, including tense and modals, can access dynamic discourse referents. By treating sloppy identity as a general feature of the resolution of anaphoric devices in discourse, we give a simple, unified treatment of the sloppy identity patterns observed with tense and modals.

Clarification requests are an important, relatively common and yet under-studied dialogue device allowing a user to ask about some feature (e.g. the meaning or form) of an utterance, or part thereof. They can take many different forms (often highly elliptical) and can have many different meanings (requesting various types of information). This thesis combines empirical, theoretical and implementational work to provide a study of the various types of clarification request that exist, give a theoretical analysis thereof, and show how the results can be applied to add useful capabilities to a prototype computational dialogue system. A series

In this paper, we argue that the grammatical scopings of quantifiers should be treated by deductive methods. In support of this position, we offer a logical treatment of almost all previously proposed substantive constraints on quantifier scoping, including those imposed by coordinate structure, control verbs, unbounded dependency constructions, anaphoric dependency and nested dependent quantifiers. These are correctly captured by a handful of linguistically motivated and logically natural inference schemes for quantification, coordination and unbounded dependency, combined with the previously motivated function introduction and elimination schemes of categorial logic. In addition, we argue that phrase-structure and transformational accounts of similar phenomena at best provide an approximation of the logical approach.

This paper addresses the problem of learning to map sentences to logical form, given training data consisting of natural language sentences paired with logical representations of their meaning. Previous approaches have been designed for particular natural languages or specific meaning representations; here we present a more general method. The approach induces a probabilistic CCG grammar that represents the meaning of individual words and defines how these meanings can be combined to analyze complete sentences. We use higher-order unification to define a hypothesis space containing all grammars consistent with the training data, and develop an online learning algorithm that efficiently searches this space while simultaneously estimating the parameters of a log-linear parsing model. Experiments demonstrate high accuracy on benchmark data sets in four languages with two different meaning representations. 1

ABSTRACT: The constraint language for lambda structures (CLLS) is an expressive language of tree de-scriptions which combines dominance constraints with powerful parallelism and binding constraints. CLLS was introduced as a uniform framework for defining underspecified semantics representations of natural language sentences, covering scope, ellipsis, and anaphora. This article presents saturation-based algo-rithms for processing the complete language of CLLS. It also gives an overview of previous results on questions of processing and complexity.

We present an approach to VP ellipsis that allows the direct derivation of source and target sentences (the former need not be unique) during semantic construction. Specific syntactic constituent structures are associated with ellipsis potential, which can then be discharged by pro-verbs like did (too). The determination of source and target sentence, which is done with semantic features in an HPSG framework, is coupled with a comprehensive analysis of ellipsis, which also handles its interaction with scope and anaphora.

We present an algorithm which assigns interpretations to several major types of ellipsis structures through a generalized procedure of syntactic reconstruction. Ellipsis structures are taken to be sequences of lexically realized arguments and/or adjuncts of an empty verbal head. Reconstruction is characterized as the specification of a (partial) correspondence relation between the unrealized head verb of an elided clause and its argument and adjuncts on one hand, and the head of a non-elided antecedent sentence and its arguments and adjuncts on the other. The algorithm generates appropriate interpretations for cases of VP ellipsis, pseudo-gapping, bare ellipsis (stripping), and gapping. It provides a uniform computational approach to a wide range of ellipsis phenomena, and it has significant advantages over several other approaches to ellipsis which have recently been suggested in the computational and linguistic literature. 1 Introduction Ellipsis structures pose an important proble...

this paper would be consistent with an identity condition defined at Surface Structure (SS), Logical Form(LF), or at the level of Discourse Representation Structure (DRS). For concreteness, we describe two possible identity conditions, at LF and DRS. 2.1 LF Recovery Condition