Guide to the Internet - The Invisible Web

The Invisible Web is the name given to the searchable databases that general internet search engines are unable to access. The reason for this is that search engine spiders and crawlers can only index web pages which are accessible via hyperlinks. The sort of information held on Invisible Web databases is usually accessed by a form/control menu, and the back-end database then creates a web page with the necessary information on it.

Finding these Invisible Web databases is quite a task, but fortunately, there are a number of good starting points for you.

Operator	Description
The Invisible Web	One of the original sites which indexed these databases, this is an excellent place to start.
Search IQ Directories	SearchIQ maintains a high quality index of speciality search engines. The SearchIQ site is a good source of information on all aspects of internet searching.
Direct Search	Direct Search is a large directory of Invisible Web search resources, organised on a single web page. It is not brilliantly organised, but it repays careful study, particularly as Gary Price continues to update the page regularly. You can search the page using your browser's Edit\|Find facility.
Lycos Searchable Databases	Something approaching 10,000 searchable databases are available via this site. The company (Intelliseek) that produces the Bullseye software maintains this index of databases for Lycos.
The Big Hub (formerly ISleuth)	The Big Hub has a well-organised index of over 3,000 subject specific databases. You can conduct a lot of your searching directly from the Big Hub site, using the forms provided.
AlphaSearch	The Calvin Library maintains directories of 'gateway' sites. Although it is not strong in the health area, it may be of value when searching in other fields. The concept is similar to the OMNI gateways in the medical field.
Infomine Multiple Database Search	This search interface will search the Infomine 'scholarly' catalogued databases for you.
WebData.com	WebData is a database portal, which categorises online databases, and providing links with a brief description.

If you are delving into specialist areas then you will need to explore the resources above. The next part of the tutorial moves further into the Invisible Web in terms of finding medical information.