26 research outputs found
Bimorphisms and synchronous grammars
We tend to think of the study of language as proceeding by characterizing the strings and structures of a language, and we think of natural language processing as using those structures to build systems of utility in manipulating the language. But many language-related problems are more fruitfully viewed as requiring the specification of a relation between two languages, rather than the specification of a single language. We provide a synthesis and extension of work that unifies two approaches to such language relations: the automata-theoretic approach based on tree transducers that transform trees to their counterparts in the relation, and the grammatical approach based on synchronous grammars that derive pairs of trees in the relation. In particular, we characterize synchronous tree-substitution grammars and synchronous tree-adjoining grammars in terms of bimorphisms, which have previously been used to characterize tree transducers. In the process, we provide new approaches to formalizing the various concepts: a metanotation for describing varieties of tree automata and transducers in equational terms; a rigorous formalization of tree-adjoining and tree-substitution grammars and their synchronous counterparts, using trees over ranked alphabets; and generalizations of tree-adjoining grammar allowing multiple adjunction.Engineering and Applied Science
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Is this article consistent with Hinchliffe's rule?
I demonstrate that Hinchliffe’s rule – if the title of a scholarly article is a yes-no question, the answer is “no” – is paradoxical, by providing an article whose title is a question whose answer is “no” if and only if its answer is “yes”.Engineering and Applied Science
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Lexical Chaining and Word-Sense-Disambiguation
Lexical chains algorithms attempt to find sequences of words in a document that are closely related semantically. Such chains have been argued to provide a good indication of the topics covered by the document without requiring a deeper analysis of the text, and have been proposed for many NLP tasks. Different underlying lexical semantic relations based on WordNet have been used for this task. Since links in WordNet connect synsets rather than words, open word-sense disambiguation becomes a necessary part of any chaining algorithm, even if the intended application is not disambiguation. Previous chaining algorithms have combined the tasks of disambiguation and chaining by choosing those word senses that maximize chain connectivity, a strategy which yields poor disambiguation accuracy in practice. We present a novel probabilistic algorithm for finding lexical chains. Our algorithm explicitly balances the requirements of maximizing chain connectivity with the choice of probable word-senses. The algorithm achieves better disambiguation results than all previous ones, but under its optimal settings shifts this balance totally in favor of probable senses, essentially ignoring the chains. This model points to an inherent conflict between chaining and word-sense-disambiguation. By establishing an upper bound on the disambiguation potential of lexical chains, we show that chaining is theoretically highly unlikely to achieve accurate disambiguation. Moreover, by defining a novel intrinsic evaluation criterion for lexical chains, we show that poor disambiguation accuracy also implies poor chain accuracy. Our results have crucial implications for chaining algorithms. At the very least, they show that disentangling disambiguation from chaining significantly improves chaining accuracy. The hardness of all-words disambiguation, however, implies that finding accurate lexical chains is harder than suggested by the literature.Engineering and Applied Science
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Eliciting and annotating uncertainty in spoken language
A major challenge in the field of automatic recognition of emotion and affect in speech is the subjective nature of affect labels. The most common approach to acquiring affect labels is to ask a panel of listeners to rate a corpus of spoken utterances along one or more dimensions of interest. For applications ranging from educational technology to voice search to dictation, a speaker’s level of certainty is a primary dimension of interest. In such applications, we would like to know the speaker’s actual level of certainty, but past research has only revealed listeners’ perception of the speaker’s level of certainty. In this paper, we present a method for eliciting spoken utterances using stimuli that we design such that they have a quantitative, crowdsourced legibility score. While we cannot control a speaker’s actual internal level of certainty, the use of these stimuli provides a better estimate of internal certainty compared to existing speech corpora. The Harvard Uncertainty Speech Corpus, containing speech data, certainty annotations, and prosodic features, is made available to the research community.Engineering and Applied Science
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Automatically Determining Versions of Scholarly Articles
Background: Repositories of scholarly articles should provide authoritative information about the materials they distribute and should distribute those materials in keeping with pertinent laws. To do so, it is important to have accurate information about the versions of articles in a collection.
Analysis: This article presents a simple statistical model to classify articles as author manuscripts or versions of record, with parameters trained on a collection of articles that have been hand-annotated for version. The algorithm achieves about 94 percent accuracy on average (cross-validated).
Conclusion and implications: The average pairwise annotator agreement among a group of experts was 94 percent, showing that the method developed in this article displays performance competitive with human experts.Engineering and Applied Science
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A Recursive Coalescing Method for Bisecting Graphs
We present an extension to a hybrid graph-bisection algorithm developed by Bui et al. that uses vertex coalescing and the Kernighan-Lin variable-depth algorithm to minimize the size of the cut set. In the original heuristic technique, one iteration of vertex coalescing is used to improve the performance of the original Kernighan-Lin algorithm. We show that by performing vertex coalescing recursively, substantially greater improvements can be achieved for standard random graphs of average degree in the range [2:0; 5:0].Engineering and Applied Science
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Foundational Issues in Natural Language Processing: Introduction
Engineering and Applied Science
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Antecedent Prediction Without a Pipeline
We consider several antecedent prediction models that use no pipelined features generated by upstream systems. Models trained in this way are interesting because they allow for side-stepping the intricacies of upstream models, and because we might expect them to generalize better to situations in which upstream features are unavailable or unreliable. Through quantitative and qualitative error analysis we identify what sorts of cases are particularly difficult for such models, and suggest some directions for further improvement.Engineering and Applied Science