Querying and searching the deep web

The term Deep Web (sometimes also called Hidden Web) [2, 5, 8] refers to the data content that is accessible through Web pages, typically via HTML forms, but is not available on static pages for indexing by search engines. Deep Web data reside in databases and are made available dynamically, as Web pages, upon a specific search or query. An example is when we query a Yellow Pages website: the generated output is the result of a query posed on an underlying database, and is not stored as static pages; such output can normally be represented in relational form.