A bootstrap technique for building domain-dependent language models

In this paper, we propose a new bootstrap technique to build domain-dependent language models. We assume that a seed corpus consisting of a small amount of data relevant to the new domain is available, which is used to build a reference language model. We also assume the availability of an external corpus, consisting of a large amount of data from various sources, which need not be directly relevant to the domain of interest. We use the reference language model and a suitable metric, such as the perplexity measure, to select sentences from the external corpus that are relevant to the domain. Once we have a sufficient number of new sentences, we can rebuild the reference language model. We then continue to select additional sentences from the external corpus, and this process continues to iterate until some satisfactory termination point is achieved. We also describe several methods to further enhancethe bootstrap technique, such as combining it with mixture modeling and class-based modeling. The performance of the proposed approach was evaluated through a set of experiments, and the results are discussed. Analysis of the convergence properties of the approach and the conditions that need to be satisfied by the external corpus and the seed corpus are highlighted, but detailed work on these issues is deferred for the future.