Computing and Information Systems - Theses

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    Discovering syntactic phenomena with and within precision grammars
    Letcher, Ned ( 2018)
    Precision grammars are hand-crafted computational models of human languages that are capable of parsing text to yield syntactic and semantic analyses. They are valuable for applications requiring the accurate extraction of semantic relationships and they also enable hypothesis testing of holistic grammatical theories over quantities of text impossible to analyse manually. Their capacity to generate linguistically accurate analyses over corpus data also supports another application: augmenting linguistic descriptions with query facilities for retrieving examples of syntactic phenomena. In order to construct such queries, it is first necessary to identify the signature of target syntactic phenomena within the analyses produced by the precision grammar in use. This is often a difficult process, however, as analyses within the descriptive grammar can diverge from those in the precision grammar due to differing theoretical assumptions made by the two resources, the use of different sets of data to inform their respective analyses, and the exigencies of implementing a large-scale formalised analyses. In this thesis, I present my research into developing methods for improving the discoverability of syntactic phenomena within precision grammars. This includes the construction of a corpus annotated with syntactic phenomena which supports the development of syntactic phenomenon discovery methodologies. Included within this context is the investigation of strategies for measuring inter-annotator agreement over textual annotations for which annotators both segment and label text---a property that traditional kappa-like measures do not support. The second facet of my research involves the development of an interactive methodology—and accompanying implementation—for navigating the alignment between dynamic characterisations of syntactic phenomena and the internal components of HPSG precision grammars associated with these phenomena. In addition to supporting the enhancement of descriptive grammars with precision grammars, this methodology has the potential to improve the accessibility of precision grammars themselves, enabling people not involved in their development to explore their internals using familiar syntactic phenomena, as well as allowing grammar engineers to navigate their grammars through the lens of analyses that are different to those found in the grammar.
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    Visualising the impact of changes to precision grammars
    Letcher, Ned ( 2010)
    The development of precision grammars is an inherently resource intensive process. In this thesis we investigate approaches for providing grammar engineers with greater feedback on the impact of changes made to grammars. We describe two different visualisations which are created by comparing parser output from two different states of the grammar. The first involves the ranking of features found in parser output according to their magnitude of change so as to provide a low-level picture of the affected parts of the grammar. The second involves performing clustering over sentences whose parsability has changed in an attempt to find related groups of changes and accompanying sentences which exemplify each locus of change. These approaches provide complimentary avenues of feedback which can hopefully improve the efficiency of the grammar engineering development process.