Towards a Semantic Annotation of English Television News - Building and Evaluating a Constraint Grammar FrameNet

Copyright 2012 by Eckhard Bick 26th Pacific Asia Conference on Language,Information and Computation pages 60–69 Towards a Semantic Annotation of English Television News - Building and Evaluating a Constraint Grammar FrameNet Eckhard Bick Institute of Language and Communication, University of Southern Denmark Campusvej 55, DK 5230 Odense M eckhard.bick@mail.dk Abstract This paper presents work on the semantic annotation of a multimodal corpus of English television news. The annotation is performed on the second-by-second- aligned transcript layer, adding verb frame categories and semantic roles on top of a morphosyntactic analysis with full dependency information. We use a rule- based method, where Constraint Grammar mapping rules are automatically generated from a syntactically anchored Framenet with about 500 frame types and 50 semantic role types. We discuss design decisions concerning the Framenet, and evaluate the coverage and performance of the pilot system on authentic news data. 1 Introduction and methodological focus Because the communicative information contained in a multi-modal corpus is distributed across different channels, it is much more difficult to process automatically than a classical text corpus. Large multi- modal corpora, in particular, constitute a challenge to quantitative-statistical exploration or even comparative qualitative studies, because they may be too big for complete inspection, let alone extensive manual mark-up. In some types of multi- modal corpora, however, such as a film- subtitle corpus, or the television news corpus that is the object of this study, aligned transcripts or captions offer at least a partial solution, because this textual layer can be used to search the corpus and extract matching sections for closer inspection, comparison or even quantitative analysis. The UCLA Communications Studies Archive (UCLA CSA) is a so-called monitor corpus of television news, where newscasts from a large number of channels are recorded daily in high-quality video mode, amounting to ~ 150.000 hours of recorded news, and growing by 100 programs a day (DeLiema, Steen & Turner 2012). To date only English language channels have been targeted, but the author's institution has plans to join the project with matching data for first the Scandinavian languages and German, then further European languages. This paper focuses on the linguistic annotation of the time-stamp-aligned textual layer of the corpus. Optimally, such annotation should address the following issues • robustness in the face of spoken language data • low error rate for basic morphosyntactic annotation • conservation/integration of non-linguistic meta-annotation (speaker, source, time ...) • unified tag system across languages to facilitate comparative studies • a semantic annotation layer to support higher-level communicative studies A well-established annotation format is the assignment of feature-attribute pairs to word tokens, expressed as tag fields and convertible to xml structures. A list of tokens with tags guarantees that all information is local and easy to filter or search, with meta-information carried along on separate lines between tokens. For the tagging/parsing task as such we have chosen the Constraint Grammar (CG) formalism (Karlsson et al. 1995, Bick 2000) which has proven robust enough for a large 60 variety of corpus annotation task, …

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