Acquisition of Morphology of an Indic Language from Text Corpus

This article describes an approach to unsupervised learning of morphology from an unannotated corpus for a highly inflectional Indo-European language called Assamese spoken by about 30 million people. Although Assamese is one of Indias national languages, it utterly lacks computational linguistic resources. There exists no prior computational work on this language spoken widely in northeast India. The work presented is pioneering in this respect. In this article, we discuss salient issues in Assamese morphology where the presence of a large number of suffixal determiners, sandhi, samas, and the propensity to use suffix sequences make approximately 50% of the words used in written and spoken text inflected. We implement methods proposed by Gaussier and Goldsmith on acquisition of morphological knowledge, and obtain F-measure performance below 60%. This motivates us to present a method more suitable for handling suffix sequences, enabling us to increase the F-measure performance of morphology acquisition to almost 70%. We describe how we build a morphological dictionary for Assamese from the text corpus. Using the morphological knowledge acquired and the morphological dictionary, we are able to process small chunks of data at a time as well as a large corpus. We achieve approximately 85% precision and recall during the analysis of small chunks of coherent text.