Search Engine Types

For the most part, Internet search tools fall into two main groups.²  The online directory is typified by "Yahoo" and "Lycos."  A second category, the search engine, is represented by other web sites such as "Hotbot" and "Alta Vista."  The difference between these two is the strategy they use to compile their site listings.  However, a third group of the search utilities are hybrids of these two approaches and combine the two into a comprehensive package.  The idea behind the hybrid search engine is to offer "the best of both worlds."

Directory-Based Search Services

For directory-based search services, the primary frame of reference is the subject matter.  The site listings are compiled and reviewed manually.  For example, Yahoo, the best known Internet Directory, dedicates staff to review and categorize site suggestions and then adds them to a specific directory on Yahoo. The directory structure is hierarchical and starts with a general subject heading such as dentistry.  Successive sub headings are more specific.  For example under Dentistry topical areas such as dental implants, fluoridation, amalgam, organizations, orthodontics, and tooth whitening are included.  These databases are comparatively small and the frequency of the updating is relatively low.

Examples of directory-based search services include:

Yahoo!
http://www.yahoo.com/
You can find almost anything at Yahoo.  This is an excellent hierarchical index that makes navigation simple. 

InfoSeek
http://www.infoseek.com/
This is another large and popular subject index.

The Search Engine

In contrast, the unmanned Search Engine completely automates the process of indexing the sites and totally removes the human component.  A software robot called a spider or crawler gathers sites from across the web as it scans pages and connects to associated links.  One particular advantage is that the spider will automatically return to the same site periodically to check for new content or new pages.

The results from this "spidering" are then saved in the engines index and serve as the basis to orient each query.  Given the automation process and the size of the Internet, these indices grow to upwards of 250 to 500 million pages.  These efficiencies enable the search engine to cover a wide variety and number of sites that are maintained current through regular visits by the robot.  The information may not be as exacting and the quantities may be voluminous compared to a directory-based site.

Use this type of resource to obtain very specific information that is current.  Robot sites also offer current linkage to other sites as referenced in the returned information.

Examples of unmanned search engines include:

Google
http://google.com
The mother of all search engines that puts the world of the Internet at your fingertips.  Results are uncanny in their accuracy and placement in rank is not altered through purchase of priority rankings.^3,4

Alta Vista
http://altavista.digital.com/
Alta Vista is a huge, fast web index provided as a service to the Internet community by Digital Equipment Corporation.  It indexes more than 30 million web pages and 14,000 Usenet news groups.

Click Here To Navigate Within Article >> Abstract Introduction Inner Workings Search Engine Types The Hybrid: Directory With Search Engine Searching the Internet Search Strategies Advanced Search Techniques Conclusion References About the Author
	Page 4 of 11
Citation Number: Vol. 2, No. 4, Page 036