Discovering Poetic Allusion in Anthologies of Classical Japanese Poems

Waka is a form of traditional Japanese poetry with a 1300year history. In this paper we attempt to semi-automatically discover instances of poetic allusion, or more generally, to find similar poems in anthologies of waka poems. The key to success is how to define the similarity measure on poems. We first examine the existing similarity measures on strings, and then give a unifying framework that captures the essences of the measures. This framework makes it easy to design new measures appropriate to finding similar poems. Using the measures, we report successful results in finding poetic allusion between two anthologies Kokinshū and Shinkokinshū. Most interestingly, we have found an instance of poetic allusion that has never been pointed out in the long history of waka research.