Structure and Systematic Searching of World Wide Web

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Structure and Systematic Searching of World Wide
Web
For more detailed information, see
http//gateway.lib.ohio-state.edu/tutor/, http//
www.lib.berkeley.edu/TeachingLib/Guides/Internet/F
indInfo.html, http//www.bedfordresearcher.com/ind
ex.cfm
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Internet and World Wide Web

• Internet is a vast collection of interconnected
  computers that can exchange information
• World Wide Web (www) is the portion of the
  internet that utilizes hypertext transfer
  protocol (http) to transfer text and graphics
  from a server computer to a client computer for
  viewing in browser

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Producing a Document for Web Availability
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Accessing a Document on Web
Internet is a communication system that allows
computers to interact with each other regardless
of their relative locations
Your computer running Internet Explorer or
Netscape program
A second computer at another location
URL
Copy of document, filename.html
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Universal Resource Locator (URL)
URL identifies the location of the computer
functioning as the server (domain name) as well
as the specific location (directory and filename)
of the requested information on that computer
URLs consisting of only the first two elements
take you to the home page (or index) of the site
from which all component pages can be accessed
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Construction of Commercial Databases
Web Index - robot computer program obtains copies
of documents and their URLS, scans for keywords,
and generates index of keywords. Example Google
Web Directory - professional editors access and
evaluate web documents, generate a subject
directory listing URLs of best documents by
categories and sub-categories for a range of
topics. Example Yahoo! And Google Directory
Specialized Database - expert editors access and
evaluate web documents, generate a subject
directory listing URLs of best documents by
categories and sub-categories for a single topic.
Many charge a fee for use and their contents are
not available through web indices or directories.
Example Chemical Abstracts Database.
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Structure of Web and Databases
No one index covers all the web - need more than
Google (3 billion)
Invisible web - databases with contents not found
by keyword searches or browsing in public web
directories dynamically generated results, fees,
etc.
Keyword searches frequently can be used to locate
invisible web directories, specialized databases
Google, enter subject web directory, or subject
database
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Ways of Searching the Web

• By subject in Web Directory using standard terms
  or "subject headings" that have been identified
  by an editor to represent the main focus of a
  document
• By keyword in Web Index using words that may
  occur somewhere in a document, such as the title,
  description (abstract) or full-text of the
  resource itself - See Google Movie at
  http//gateway.lib.ohio-state.edu/ viewlets/
  basicgoogle.viewlet/basicgoogle_viewlet_swf.html

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Systematic Web Searches
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http//gateway.lib.ohio-state.edu/tutor/les4/pg3ma
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Subject Searching

• Best use use this method when your research
  topic is broad (such as "substance abuse") or
  ambiguous (such as "Columbus" city in Ohio or
  Christopher?)
• Requirements translate your search concepts into
  subject vocabulary used by the database
  (different for each database)

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Vary with database
Consecutive selections from hierarchy
Sub-topic
Subject
browse
Sub-sub-topic
Sub-topic
browse
Sub-sub-topic
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Keyword Searching

• Best use use keyword searching when your topic
  is specific (such as "substance abuse during
  pregnancy") or not much has been written on it
• Requirements must construct the search using
  operators, quotation marks, truncation, and/or
  parentheses

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Constructing a Keyword Search

• Use operators (Boolean or math) to connect search
  terms to accomplish specific results
• Use quotation marks to locate unique phrases
  "affirmative action"
• Use truncation to obtain word variants from a
  stem cat, cats child, children etc.
• Use parentheses to organize complex search
  statements combinations of related terms

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Use of Operators Boolean (words) or Mathematical
Symbols ( and -) to obtain specific results
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Boolean Operators
Narrows search
Broadens search
Narrows search
http//www.lib.berkeley.edu/TeachingLib/Guides/Int
ernet/Boolean.pdf
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Use of Quotation Marks for Searching for Phrases
- some databases use quotation marks to enclose
an exact phrase, others use Boolean operators
such as NEAR or ADJ to indicate proximity of
terms. (NOTE these Boolean operators are NOT
supported by all databases.)
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Comparison of Operators
To find recipes for peanut butter cookies, for
example, the most efficient search statement is
Using Boolean operators "peanut butter cookies"
AND recipes Using mathematical operators
"peanut butter cookies"  recipes
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Use of Truncation Symbols for Word Variants from
a Given Stem

• Some databases require truncation symbol,
  question mark (?) or asterisk () at the end of
  word roots to find plural and related forms
• Search statement, substance NEAR abuse, will
  find substance abuse, substance abuser, abuse of
  controlled substances
• Google) has stemming feature that automatically
  searches for variant word forms such as plurals,
  etc. (not totally reliable)

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Use of Parentheses to Group Search Terms
To create more complex search statements use
parentheses to group search words that should be
treated in the same way. This is sometimes called
"nesting" and is a handy way to incorporate
synonyms or related terms into your search.
You may link synonyms or related terms for each
of your search concepts into a "cluster" using
the OR operator. Enclose a cluster within
parentheses. You can then combine clusters using
the Boolean operator AND.
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Searches Involving Synonyms

• Related terms can be grouped using parentheses as
  on previous slide
• Google has a limited automatic synonym search
  invoked by tilde sign ("") immediately in front
  of the keyword
• food facts gives results including food facts
  as well as nutrition and cooking information
  (still in development)

Google Help
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Vary with database
consecutive selections from hierarchy
Search Topic
Truncation (,?)
finds
Word variants from stem
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Keyword Multi-Search
Subject Search
Keyword Search
Search tool depends on database
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Cont'd

• Meta-searcher - "Meta" means "more
  comprehensive." A meta-searcher is a convenient
  tool that allows you to construct a search and
  then forward it to many different Web Indexes and
  Directories at once. They are a quick and easy
  way to expand your search, particularly when
  other tools don't find what you are looking for.
  Like Web Indexes, they work best for specific,
  multi-word searches.

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Links to On-Line Resources

• Annotated list with links to 12 search engines
  for web indexes http//www.bedfordresearcher.com/
  manuals/web/use_search.cfm
• Annotated list with links to 9 Web Directories
  http//www.bedfordresearcher.com/
  manuals/web/use_directory.cfm

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Cont'd

• Annotated list of 10 meta search engines with
  links http//www.bedfordresearcher.com/
  manuals/web/use_meta.cfm
• See http//www.lib.duke.edu/texis/databases/ and
  http//www.lib.duke.edu/chem for listings and
  links to databases including subscription
  databases that are available at Duke

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Strategies for Keyword Searches

• Keep phrases short. Longer phrases are less
  likely to be found. For example, search for
  "substance abuse" AND treatment, not "substance
  abuse treatment programs."
• Perform your search in stages. Iterative process
  - first, search for the most important concepts
  or the most unique words. Then refine.

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Refining a Search
Most online searching is "iterative," requiring
that you continually refine or tune your search.
Here are some proven strategies for adjusting
keyword searches that find too much or too
little.
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Some Search Engines Suggest Refinements
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Expanding Results

• As you review results, watch for new or alternate
  terms. Incorporate them into your next search.
  For example, use "chemical dependency" as well as
  "substance abuse." Connect these search terms
  with the OR operator to expand your results
• For databases that utilize stemming (Google), use
  the tilde() operator in front of keywords to
  expand results to include synonyms

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Narrowing Results

• Most online databases also allow you to limit
  your search results by language, time , etc. see
  http//www.google.com/help/ refinesearch.html
• In a Web Index you may also limit your search to
  specific elements present in Web pages such as
  page titles, URLs, etc. see http//www.google.com/
  help/operators.html

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