International Journal of Computer Applications
World Wide Web (WWW) has more and more online web databases which can be searched through their web query interfaces. The number of web databases has reached 25 million according to a recent survey. All the web databases make up the deep web (hidden web or invisible web). Often the retrieved information (query results) is enwrapped in web pages in the form of data records. These special web pages are generated dynamically and are hard to index by traditional crawler-based search engines, such as Google and Yahoo.