The Deep Web

The Deep Web (also called the Deepnet,[1] Invisible Web,[2] or Hidden Web[3]) is World Wide Web content that is not part of the Surface Web, which is indexed by standard search engines. It should not be confused with the dark Internet, the computers that can no longer be reached via the Internet, or with a Darknet distributed filesharing network, which could be classified as a smaller part of the Deep Web. There is concern that the deep web can be used for serious criminal activity.[4]

Mike Bergman, founder of BrightPlanet and credited with coining the phrase,[5] said that searching on the Internet today can be compared to dragging a net across the surface of the ocean: a great deal may be caught in the net, but there is a wealth of information that is deep and therefore missed.[6] Most of the Web's information is buried far down on dynamically generated sites, and standard search engines do not find it. Traditional search engines cannot "see" or retrieve content in the deep Web—those pages do not exist until they are created dynamically as the result of a specific search. As of 2001, the deep Web was several orders of magnitude larger than the surface Web.[7]

Contents [hide]

1 Size

2 Naming

3 Deep resources

4 Accessing

5 Crawling the Deep Web

6 Classifying resources

7 Future

8 See also

9 References

10 Further reading

11 External links

Size[edit]

Estimates based on extrapolations from a study done at University of California, Berkeley in 2001[7] speculate that the deep Web consists of about 7.5 petabytes. More accurate estimates are available for the number of resources in the deep Web: research of He et al. detected around 300,000 deep web sites in the entire Web in 2004,[8] and, according to Shestakov, around 14,000 deep web sites existed in the Russian part of the Web in 2006.[9]

Naming[edit]

Bergman, in a seminal paper on the deep Web published in the Journal of Electronic Publishing, mentioned that Jill Ellsworth used the term invisible Web in 1994 to refer to websites that were not registered with any search engine.[7] Bergman cited a January 1996 article by Frank Garcia:[10]

It would be a site that's possibly reasonably designed, but they didn't bother to register it with any of the search engines. So, no one can find them! You're hidden. I call that the invisible Web.

Another early use of the term Invisible Web was by Bruce Mount and Matthew B. Koll of Personal Library Software, in a description of the @1 deep Web tool found in a December 1996 press release.[11]

The first use of the specific term Deep Web, now generally accepted, occurred in the aforementioned 2001 Bergman study.[7]

Deep resources[edit]

Deep Web resources may be classified into one or more of the following categories:

Dynamic content: dynamic pages which are returned in response to a submitted query or accessed only through a form, especially if open-domain input elements (such as text fields) are used; such fields are hard to navigate without domain knowledge.

Unlinked content: pages which are not linked to by other pages, which may prevent Web crawling programs from accessing the content. This content is referred to as pages without backlinks (or inlinks).

Private Web: sites that require registration and login (password-protected resources).

Contextual Web: pages with content varying for different access contexts (e.g., ranges of client IP addresses or previous navigation sequence).

Limited access content: sites that limit access to their pages in a technical way (e.g., using the Robots Exclusion Standard, CAPTCHAs, or no-cache Pragma HTTP headers which prohibit search engines from browsing them and creating cached copies.[12])

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