Week 3: Week 3:
MetaSearch EnginesMetaSearch Engines
Click here for Word handoutTom Johnson
Boston University - Dept. of [email protected]
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MetaSearch Engines: Definition
You submit keywords in search box Engine transmits search simultaneously to
several individual search engines and their databases of web pages.
Results back from all the search engines queried, usually deleting duplicates
Meta-search engines do not own a database of Web pages; they send your search terms to the databases maintained for other search engines.
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How do you know if your search terms will "work"?
Search protocol (the way you enter search keywords) is far from standardized
Almost all accept " " as causing a phrase A few accept Boolean AND, OR, and NOT. Fewer accept ( ) to group terms. Some only accept + or -. Some default to OR, some to AND Some take * to truncate. Other stem
automatically
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Determining the usefulness of any meta-search engine?
Which search engines they send your search terms to (size, content, number of search engines, you ability to choose the search engines you prefer. All of them search subject directories as well as search engines and intermix results from all.)
How they handle your search terms and search syntax (Boolean operators, phrases, and defaults they impose);
How they display results (ranking; aggregated into one list, or with each search engine's results reported separately)
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Use metasearch, but cautiously Meta-search engines only spend a short time
in each database; often retrieve <10% of any of the results in any of the databases queried.
Most meta-searchers simply pass your search terms along; if search contains more than one or two words or very complex logic, most of that will be lost.
Quantity in results does not equal satisfaction. Look for meta-search engines that also send
your terms to selective or odd databases like WebCrawler, Thunderstone, Direct Hit, and WhatUSeek.
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Types of Search Engines
Search Engines & Meta-Search Engines
Subject Directories Subject Guides Specialized Databases
The Invisible Web Edgar
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Types of Search Engines: Search Engines & Meta-Search Engines Full-text of selected Web pages Search by keyword, trying to match words in pages No browsing, no subject categories Databases compiled by "spiders" (computer-robot
programs) with minimal human oversight Search-Engine size: from small and specialized to 90+
percent of the indexable Web Meta-Search Engines quickly, superficially search
several individual search engines at once. Return results compiled into a sometimes convenient format.
CAVEAT: Only catch about 10% of search results in any of the search engines they visit.
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Types of Search Engines Search Engines & Meta-Search Engines
Examples: Alta Vista, Northern Light, Infoseek, Fast
Search Other search engines:
Hotbot, Lycos, Excite Meta-Search Engines:
Metacrawler, Inference Find, Dogpile, Metafind
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Types of Search Engines:Subject Directories
Characteristics: Hand-selected sites picked by editors, more or less
carefully Organized into hierarchical subject categories Often annotated with descriptions (not in Yahoo!) Browse subject categories or search using broad,
general terms NO full-text of documents. Can search only the subject
categories and descriptions
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Types of Search Engines:Subject Directories
Examples: Librarians' Index, Infomine, Britannica's Internet
Guide, Yahoo!, Galaxy Other subject directories: Scout Report Signpost, Looksmart, Lycos's A2Z
and Top 5% Built into Infoseek, Excite Most university libraries maintain subject
directories
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Types of Search Engines:Subject Guides
Characteristics: Web pages of collections of hypertext links on a
subject Compiled by "expert" subject specialists,
agencies, associations, and hobbyists Locate through special guides to guides or
subject directories or sometimes among search engine keyword search results
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Types of Search Engines:Subject Guides
Characteristics: Web pages of collections of hypertext links on a
subject Compiled by "expert" subject specialists,
agencies, associations, and hobbyists Locate through special guides to guides or
subject directories or sometimes among search engine keyword search results
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Types of Search Engines:Subject Guides
Examples: Guides to guides:
Argus Clearinghouse WWW Virtual Library
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Types of Search Engines:Specialized Databases
Characteristics: The Web provides access through a search box into
the contents of a database in a computer somewhere
Can be on any topic, can be trivial, commercial, task-specific, or a rich treasure devoted to your topic
Locate by special guides to databases, in Librarian's Index, Yahoo!, and sometimes by keyword searching general search engines
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Types of Search Engines:Specialized Databases
Examples: Sites listing lots of Databases
Search.com www.search.com The Invisible Web www.about.com Edgar www.edgar-online.com FECInfo www.fecinfo.com Adobe PDF files searchpdf.adobe.com
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A good place to start
BEST General Web Page SEARCH ENGINEShttp://www.lib.berkeley.edu/TeachingLib/Guides/Internet/SearchEngines.html
A Graduated Approach in 5 Stepshttp://www.lib.berkeley.edu/Help/search.html
Search Engine Guide http://www.searchengineguide.com 3,600+ search engines in its index. Will take you to search engines that target specific industries or topics, including 67 for "News and Media." This homepage also has a link to its mailing list, a good listserv that helps you stay on top of new developments in the metasearch world.