Creative Discovery in Lexical Ontologies

Creative Discovery in Lexical Ontologies Tony VEALE Dept. of Computer Science Belfield, Dublin, Ireland, D4 Tony.Veale@UCD.ie Nuno SECO, Jer HAYES Dept. of Computer Science Belfield, Dublin, Ireland, D4 {nuno.seco, jer.hayes}@UCD.ie Abstract Compound terms play a surprisingly key role in the organization of lexical ontologies. However, their inclusion forces one to address the issues of completeness and consistency that naturally arise from this organizational role. In this paper we show how creative exploration in the space of literal compounds can reveal not only additional compound terms to systematically balance an ontology, but can also discover new and potentially innovative concepts in their own right. 1 Introduction Broad-coverage lexical knowledge-bases like WordNet (Miller et al., 1990) generally contain a large number of compound terms, many of which are literal in composition. These compounds are undoubtedly included for a reason, yet the idea that literal compounds might actually be essential to WordNet’s usefulness may strike some as heretical on at least two fronts: first, the lexicon is a finite resource, while the space of compounds is potentially infinite; and at any rate, literal compounds can be created as needed from purely compositional principles (Hanks, 2004). However, these retorts are valid only if we view WordNet as a dictionary, but of course it is much more than this. WordNet is a lexical ontology, and ultimately, ontologies derive a large part of their functionality from their structure. So, while the meaning of literal compounds like Greek-deity and animal-product may well be predictable from compositional principles alone, such concepts still serve an important organizational role in WordNet by adding much needed structure to the middle ontology. Having conceded the importance of such compounds, one is forced to address the issues of completeness and consistency that then arise from their inclusion. Completeness suggests that we strive to include as many literal compounds as are sensible, if they enhance the organization of the ontology or if there is evidence that they are in common usage in the language. Systematicity is a related issue that arises when a group of existing compounds suggests that another should also exist for the ontology to be consistent. For instance, the existence of Greek-deity, Greek-alphabet and Hebrew-alphabet leads to the hypothesis that Hebrew-deity should also exist if WordNet is to be both consistent and symmetric in its treatment of different cultural groupings. Indeed, because literal compounds like these arise from the yoking together of two different ontological branches into one, compounding represents an important contextualization device in the design of ontologies, allowing lexical elements to be logically grouped into clusters or families that share important dimensions of meaning. This clustering facilitates both automated reasoning by machines (such as the determination of semantic similarity based on taxonomic distance) and effective browsing by humans. Sometimes this yoking results in a compound that, following Boden (1990) and Wiggins (2003), deserves to be called “creative”, because it exhibits both novelty and value. Novelty can be measured along either a psychological or a historical dimension, while utility is …

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