Crawling for domain-specific hidden Web resources

The Hidden Web, the part of the Web that remains unavailable for standard crawlers, has become an important research topic during recent years. Its size is estimated to 400 to 500 times larger than that of the publicly indexable Web (PIW). Furthermore, the information on the hidden Web is assumed to be more structured, because it is usually stored in databases. In this paper, we describe a crawler which starting from the PIW finds entry points into the hidden Web. The crawler is domain-specific and is initialized with pre-classified documents and relevant keywords. We describe our approach to the automatic identification of Hidden Web resources among encountered HTML forms. We conduct a series of experiments using the top-level categories in the Google directory and report our analysis of the discovered Hidden Web resources.