Mining the Web for Idiomatic Expressions Using Metalinguistic Markers

In this paper, methods for identification and delimitation of idiomatic expressions in large Web corpora are presented. The proposed methods are based on the observation that idiomatic expressions are sometimes accompanied by metalinguistic expressions, e.g. the word “proverbial”, the expression “as they say” or quotation marks. Even though the frequency of such idiom-related metalinguistic markers is not very high, it is possible to identify new idiomatic expressions with a sufficiently large corpus (only type identification of idiomatic expressions is discussed here, not the token identification). In this paper, we propose to combine infrequent but reliable idiom-related markers (such as the word “proverbial”) with frequent but unreliable markers (such as quotation marks). The former could be used for the identification of idiom candidates, the latter – for their delimitation. The experiments for the estimation of recall upper bound of the proposed methods are also presented in this paper. Even though the paper is concerned with identification and delimitations of Polish idiomatic expressions, the approaches proposed here should also be feasible for other languages with sufficiently large web corpora, English in particular.