WordNet and FrameNet as Complementary Resources for Annotation

WordNet and FrameNet are widely used lexical resources, but they are very different from each other and are often used in completely different ways in NLP. In a case study in which a short passage is annotated in both frameworks, we show how the synsets and definitions of WordNet and the syntagmatic information from FrameNet can complement each other, forming a more complete representation of the lexical semantic of a text than either could alone. Close comparisons between them also suggest ways in which they can be brought into alignment. 1 Background and motivation FrameNet and WordNet are two lexical databases that are widely used for NLP, often in conjunction. Because of their complementary designs they are obvious candidates for alignment, and an exploratory research project within the larger context of the semantic annotation of the the American national Corpus is currently underway. We give specific illustrative examples of annotations against both resources, highlighting their different contributions towards a rich semantic analysis. WordNet (WN):1 (Fellbaum, 1998), is a large electronic lexical database of English. Originally conceived as a full-scale model of human semantic organization, it was quickly embraced by the Natural Language Processing (NLP) community, a development that guided its subsequent growth and design. WordNet has become the lexical database of choice for NLP and has been incorporated into other language tools, including VerbNet (Kipper et al., 2000) and OntoNotes (Hovy et al., 2006). Numerous on-line dictionaries, including Google’s “define” function, rely significantly on WordNet. WordNet’s coverage is sometimes criticized as being too fine-grained for automatic processing, though its inventory is not larger than that of a standard collegiate dictionary. But the present limitation of automatic WSD cannot be entirely blamed on existing systems; for example, Fellbaum and Grabowski (1997) http://wordnet.princeton.edu have shown that humans, too, have difficulties identifying context-appropriate dictionary senses. One answer is clearly that meanings do not exist outside contexts. Furthermore, although WN does contain “sentence frames” such as “Somebody —-s something” for a transitive verb with a human agent, it provides little syntagmatic information, except for what can be gleaned from the example sentences. WordNet’s great strength is its extensive coverage, with more than 117,000 synonym sets (synsets), each with a definition and relations to other synsets covering almost all the general vocabulary of English. FrameNet (FN):2 (Fontenelle, 2003) is a lexical resource organized not around words per se, but semantic frames (Fillmore, 1976): characterizations of events, relations, and states which are the conceptual basis for understanding groups of word senses, called lexical units (LUs). Frames are distinguished by the set of roles involved, known as frame elements (FEs). Much of the information in the FrameNet lexicon is derived by annotating corpus sentences; for each LU, groups of sentences are extracted from a corpus, sentences which collectively exemplify all of the lexicographically relevant syntactic patterns in which the LU occurs. A few examples of each pattern are annotated; annotators not only mark the target word which evokes the frame in the mind of the hearer, but also mark those phrases which are syntactically related to the target word and express its frame elements. FrameNet is much smaller than WordNet, covering roughly 11,000 LUs, but contains very rich syntagmatic information about the combinatorial possibilities of each LU. Given these two lexical resources with different strengths, it seems clear that combining WN and FN annotation will produce a more complete semantic representation of the meaning of a text than either could alone. What follows is intended as an example of how they can usefully be combined. 2 Case Study: Aegean History The text chosen for this study is a paragraph from the American National Corpus3 (Ide et al., 2002), from the Berlitz travel guide to Greece, discussing the history of http://framenet.icsi.berkeley.edu http://www.americannationalcorpus.org