http://www.touro.edu/library/GuidesTutorials/FindWebResources.asp
Touro College Libraries
Finding Web Resources
There are three major categories of tools for finding information on the
Web. They are subject directories and search engines, and deep Web
resources. Each is useful for different types of queries. Be
sure you know their differences.
Subject directories
Subject directories are databases of links selected and organized into
subject categories by site creators or evaluators. Most are searchable.
They are good for general research queries and when you want sites recommended
by experts.
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There are two basic types of subject directories. Academic and professional
directories are created and maintained by subject experts to support the
needs of researchers. Commercial directories and portals cater to
the general public and compete for traffic. Be sure to use the type
of directory that appropriately meets your needs.
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Subject directories differ significantly in selectivity. Try to read
the policies of the directories you visit. This can be a challenge
since not all directories disclose their policies nor the names and qualifications
of their site reviewers. This is especially true of commercial directories.
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Many people bypass subject directories and go straight to search engines.
However, remember that academic and professional directories contain carefully
chosen and annotated links. Do not overlook them when searching for
quality on the Web.
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Our Web
& Search Sites directory has lists of general and subject-specific
subject directories.
Search engines
Search engines are searchable databases of files collected by computer
programs. Their indexes are generated from the collected files (title,
full text, size, URL, etc.). They are good for targeted and complex
queries.
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There are three components to search engines. Programs called wanderers,
crawlers, robots, worms, spiders, etc., traverse the Web from link to link,
identifying and reading pages. Indexes or databases have copies of
Web pages gathered by the programs. Search engine interfaces or software
enable users to query the indexes and usually return results in relevancy
ranked order.
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When you use a search engine, you will have a better chance of success
if you understand some fundamental search techniques. These techniques
include the use of truncation, phrases in quotation, boolean logic, and
field searching. Read about Search
Techniques and how to apply them.
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Search engines do not involve selection criteria. However, evaluation
may be applied by ranking results (by popularity, etc.). Therefore,
it is up to you to carefully evaluate the resources you find and determine
their appropriateness for research. Read Evaluating
Web Resources for things to consider in your analysis.
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Our Web
& Search Sites directory has lists of general and subject-specific
search engines.
Content on the deep Web
The deep Web refers to content in both proprietary (purchased or subscription)
and public domain (free) databases. It includes dynamically changing
information (news, job postings, airline flights, stock prices, etc.) and
static, fixed Web pages (phone books, dictionary definitions, full-text
periodical articles, etc.). The content of the deep Web is 500 times
the size of the surface Web. When you search a deep Web database,
you get back a Web page with results created dynamically (on-the-spot)
and specific to your query. These pages are not linked since they
did not exist before your search and they cease to exist after they are
sent to you. Search engines cannot see nor find them.
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Deep Web content consists of two types of information. Databases
created by programs (Access, Oracle, SQL Server, DB2, etc.) contain information
stored in tables that is accesible only by query. Non-textual files
(graphical files, software, Portable Document Format [PDF], Musical Instrument
Digital Interface [MIDI], etc.) that can be accessed directly. Many
search engines (AltaVista,
Excite,
HotBot,
Lycos,
etc.) have separate search options for locating these files. Others
(Google, etc.) integrate them into their general search service.
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Topical coverage on the deep Web is extremely varied and fluid as the number
of databases proliferate. When dealing with the deep Web, remember
that many databases are searchable from their own sites. Good subject
directories will link to these sites and search engines will find them.
Once you connect to these sites, you can search their databases.
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Our Web
& Search Sites directory lists deep Web tools on its subject
directory and search engine pages.
Learning More and Keeping Up
To learn more about subject engines, search engines, and deep Web resources,
review the following.
To keep up with the rapidly changing World Wide Web, regularly consult
the following.
Go to the top of the page.