Deep Web Search and Vertical Search Engine
Nowadays, the main or the most general approach for finding and accessing information sources is searching queries over general search engines such as Google, Yahoo, or Bing. However, these search engines do not cover all the data available on the Web. In addition, none of these search engines cover all the web pages existing on the Web, they miss huge data behind web search forms. This data is defined as hidden web or deep web which is not accessible through search engines. It is estimated that deep web contains data in a scale several times bigger than the data accessible through search engines, which is referred to as surface web. Although this information on deep web could be accessed through their own interfaces, finding and querying all the interesting sources of information that might be useful could be a difficult, time – consuming and tiring task.