Conventional Metaphor and the Lexicon

Metaphor and other forms of non-literal language are essential parts of language which have direct bearing on theories of lexical semantics. Neither narrow theories of lexical semantics, nor theories relying solely on world knowledge are sufficient to account for our ability to generate and interpret non-literal language. This paper presents an emerging approach that may provide such an account. This approach is based on systematic representations that capture non-literal language conventions, and mechanisms that can dynamically understand and learn new uses as they are encountered. 1 I n t r o d u c t i o n In tradit ional approaches to Lexical Semantics a whole host of phenomena have been largely banished from consideration. Among the unwelcome phenomena have been irony, sarcasm, metaphor, metonymy, indirect requests, and productive idioms. These phenomena have been relegated to various areas of pragmatics, context, and world knowledge. Implicit in this banishment is the assertion that the mechanisms and knowledge necessary to account for these uses are fundamentally different from those used in ordinary semantic interpretation. Moreover, this additional knowledge is generally held to be that of a more general common-sense conceptual kind. This point of view has a number of useful properties. Firstly, it severely limits the range of uses tha t need to be accounted for by lexicM semantics. Therefore, the sheer amount of work faced by the lexical semanticist can be reduced. The job of lexical semantics is essentially finished once the semantics of a word's literal meaning have been adequately represented and tied to the observed syntactic behavior of the word. The second impor tant property (really just a different view of the first) is the notion that a lexicon with a relatively small fixed number of senses per word can still hope to account for the much larger number of senses actually encountered in practice. This follows from the fact tha t the range of senses is tied to the amount of real world knowledge in the knowledge-base, and the ability of the extra-linguistic mechanisms to make use of this knowledge. It is this second property that is most relevant to approaches to computat ional lexical semantics. This state of affairs can be summarized as follows. • Lexical semantics is limited to individual lexical items paired with literal meanings. • Non-literal uses are dealt with by mechanisms that are not required for otherwise "normal" semantic processing. (Among the methods that have been used are analogical matchers, planners, and spreading activation.)