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Invisible Web: What it is, Why it exists, How to find it, and...

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Saved by 86 people (-57 private), first by anonymouse user on 2006-03-02


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on 2008-03-12 by greenar

不能被SE发现的Internet数据叫做Invisible Web，或者叫Deep Web

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Rarely are such pages stored anywhere: it is easier and cheaper to dynamically generate the answer page for each query than to store all the possible pages containing all the possible answers to all the possible queries people could make to the database.

Highlighted by jackie

If access to a web pages requires typing, web crawlers encounter a barrier they cannot go beyond. They cannot search our online catalogs and they cannot enter a password or login.

Highlighted by jackie

Google Scholar is only able to provide citations to journal contents for which its crawlers can find stable llinks. It cannot construct searches or enter passwords to go into passworded, copyright-protected articles in many publishers' databases.

Highlighted by jackie

In some experiments conducted at UC Berkeley, we estimate that Google Scholar accesses about 10% of all we subscribe to for our students, faculty, staff, and users present on campus. Think about the millions of articles in Lexis/Nexis, the many thousands of articles indexed in privately licensed databased libraries buy the rights for their users to read (e.g., Sociological Abstracts, ERIC, PscyhInfo, JSTOR, INSPEC). At Berkeley we subscribe ot about 200 of these.

Highlighted by jackie

in addition to what you find in search engine results (including Google Scholar) and most web directories, there are these gold mines you have to search directly. This includes all of the licensed article, magazine, reference, news archives, and other research resources that libraries and some industries buy for those authorized to use them.

Highlighted by jackie

The "visible web" is what you see in the results pages from general web search engines. It's also what you see in almost all subject directories. The "invisible web" is what you cannot retrieve ("see") in the search results and other links contained in these types of tools.

Highlighted by sborowski

The contents of these are not freely available: libraries and corporations buy the rights for their authorized users to view the contents. If they appear free, it's because you are somehow authorized to search and read the contents (library card holder, member of the company, etc.).

Highlighted by jackie