Approximate Factoring for A ∗ Search

We present a novel method for creating A ∗ estimates for structured search problems. In our approach, we project a complex model onto multiple simpler models for which exact inference is efficient. We use an optimization framework to estimate parameters for these projections in a way which bounds the true costs. Similar to Klein and Manning (2003), we then combine completion estimates from the simpler models to guide search in the original complex model. We apply our approach to bitext parsing and lexicalized parsing, demonstrating its effectiveness in these domains.