Information extraction systems extract structured data from natural language text, to support richer querying and analysis of the data than would be possible over the unstructured text. Unfortunately, information extraction is a computationally expensive task, so exhaustively processing all documents of a large collection might be prohibitive. Such exhaustive processing is generally unnecessary, though, because many times only a small set of documents in a collection is useful for a given information extraction task. Therefore, by identifying these useful documents, and not processing the rest, we could substantially improve the efficiency and scalability of an extraction task. Existing approaches for identifying such documents often miss useful documents and also lead to the processing of useless documents unnecessarily, which in turn negatively impacts the quality and efficiency of the extraction process. To address these limitations of the state-of-the-art techniques, we propose a principled, learning-based approach for ranking documents according to their potential usefulness for an extraction task. Our low-overhead, online learning-to-rank methods exploit the information collected during extraction, as we process new documents and the fine-grained characteristics of the useful documents are revealed. Then, these methods decide when the ranking model should be updated, hence significantly improving the document ranking quality over time. Our experiments show that our approach achieves higher accuracy than the state-of-the-art alternatives. Importantly, our approach is lightweight and efficient, and hence is a substantial step towards scalable information extraction.
['Pablo Barrio', 'Gonçalo Simões', 'Helena Galhardas', 'Luis Gravano']
Learning to Rank Adaptively for Scalable Information Extraction