Robert Malouf

Satisfying constraints on extraction and adjunction

In this paper, we present a unified feature-based theory of complement, adjunct, and subject extraction, in which there is no need either for valence reducing lexical rules or for phonologically null traces. Our analysis rests on the assumption that the mapping between argument structure and valence is defined by realization constraints which are satisfied by all lexical heads. Arguments can be realized as local dependents, in which case they are selected via the heads valence features. Alternatively, arguments may be realized in a long-distance dependency construction, in which case they are selected via the heads slash features. Furthermore, we argue that English post-verbal adjuncts, as well as complements, are syntactic dependentsselected by the verb, thus providing a uniform analysis of complement andadjunct extraction. Finally, we show that our analysis provides analternative treatment of subject extraction and we offer a new account of thethat-trace effect.

The Alpino Dependency Treebank

In this paper we present the Alpino Dependency Treebank and the tools that we have developed to facilitate the annotation process. Annotation typically starts with parsing a sentence with the Alpino parser, a wide coverage parser of Dutch text, The number of parses that is generated is reduced through interactive lexical analysis and constituent marking. A tool for on line addition of lexical information facilitates the parsing of sentences with unknown words. The selection of the best parse is done efficiently with the parse selection tool. At this moment, the Alpino Dependency Treebank consists of about 6,000 sentences of newspaper text that are annotated with dependency trees. The corpus can be used for linguistic exploration as well as for training and evaluation purposes.

Alpino: Wide-coverage Computational Analysis of Dutch

Alpino is a wide-coverage computational analyzer of Dutch which aims at accurate, full, parsing of unrestricted text. We describe the head-driven lexicalized grammar and the lexical component, which has been derived from existing resources. The grammar produces dependency structures, thus providing a reasonably abstract and theory-neutral level of linguistic representation. An important aspect of wide-coverage parsing is robustness and disambiguation. The dependency relations encoded in the dependency structures have been used to develop and evaluate both hand-coded and statistical disambiguation methods.

The order of prenominal adjectives in natural language generation

The order of prenominal adjectival modifiers in English is governed by complex and difficult to describe constraints which straddle the boundary between competence and performance. This paper describes and compares a number of statistical and machine learning techniques for ordering sequences of adjectives in the context of a natural language generation system.

Efficient feature structure operations without compilation

One major obstacle to the efficient processing of large wide coverage grammars in unification-based grammatical frameworks such as HPSG is the time and space cost of the unification operation itself. In a grammar development system it is not appropriate to address this problem with techniques which involve lengthy compilation, since this slows down the edit-test-debug cycle. Nor is it possible to radically restructure the grammar. In this paper, we describe novel extensions to an existing efficient unification algorithm which improve its space and time behaviour (without affecting its correctness) by substantially increasing the amount of structure sharing that takes place. We also describe a fast and automatically tunable pre-unification filter (the ‘quick check’) which in practice detects a large proportion of unifications that if performed would fail. Finally, we present an efficient algorithm for checking for subsumption relationships between two feature structures; a special case of this gives a fast equality test. The subsumption check is used in a parser (described elsewhere in this issue) which ‘packs’ local ambiguities to avoid performing redundant sub-computations.

Maximal Consistent Subsets

Default unification operations combine strict information with information from one or more defeasible feature structures. Many such operations require finding the maximal subsets of a set of atomic constraints that are consistent with each other and with the strict feature structure, where a subset is maximally consistent with respect to the subsumption ordering if no constraint can be added to it without creating an inconsistency. Although this problem is NP-complete, there are a number of heuristic optimizations that can be used to substantially reduce the size of the search space. In this article, we propose a novel optimization, leaf pruning, which in some cases yields an improvement in running time of several orders of magnitude over previously described algorithms. This makes default unification efficient enough to be practical for a wide range of problems and applications.

Implicative organization facilitates morphological learning

One dimension of this task is segmentation. For example, how can learners separate the stems from the affixes that signal a particular morphosyntactic property? If this information was all that learners had, they might hypothesize that zavod has the lexical meaning ‘factory’, and the –ov suffix signals genitive plural. A large body of experimental research addresses this syntagmatic, structural challenge of identifying recurrent partial forms (e.g., Saffran et al. 1996; Finley and Newport 2011; Aslin and Newport 2012). However, there is also a paradigmatic aspect to the problem. For example, the table below shows some alternative possibilities for how a plural form might be realized with different cases in Russian (Baerman et al. 2009).

Computational Lexical Analysis of the Language Commonly Used to Describe Gout.

To characterize the current language that is used in describing and defining gout, its symptoms, and its treatment by reviewing recent publications in rheumatology and determining how word choice may, or may not, be reflective of recent scientific developments in gout specifically.

Using an open-source unification-based system for CL/NLP teaching

We demonstrate the open-source LKB system which has been used to teach the fundamentals of constraint-based grammar development to several groups of students.

Acoustic differences in morphologically-distinct homophones

ABSTRACT Previous work demonstrates that a words status as morphologically-simple or complex may be reflected in its phonetic realisation. One possible source for these effects is phonetic paradigm uniformity, in which an intended words phonetic realisation is influenced by its morphological relatives. For example, the realisation of the inflected word frees should be influenced by the phonological plan for free, and thus be non-homophonous with the morphologically-simple word freeze. We test this prediction by analysing productions of forty such inflected/simple word pairs, embedded in pseudo-conversational speech structured to avoid metalinguistic task effects, and balanced for frequency, orthography, as well as segmental and prosodic context. We find that stem and suffix durations are significantly longer by about 4–7% in fricative-final inflected words (frees, laps) compared to their simple counterparts (freeze, lapse), while we find a null effect for stop-final words. The result suggests that wordforms influence production of their relatives.