Search Engines

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Search Engines
Information
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Problems with searching the Web

• Unregulated growth
• no standard indexing
• slow response time
• no validity check (peer review?)
• No way to determine if changed since last
  accessed site
• no way to reject irrelevant documents

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Many Search engines

• Search Engines are Computer programs
• They move through the Web collecting
  Key-words
• On - screen directions are easy to follow
• Results presented as a list of sites
• Ranked in order of relevance

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Four types of search engines

• 1.SUBJECT Directories like Yahoo.com.au
• 2.AUSTRALIAN search tool like Anzwers.com.au
• 3.META SEARCH Tool like Dogpile.com.
• 4. KEY WORD search like Altavista.yellowpages.com.
  au

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Relevance and Ranking

• Relevance due to a formulae
• Each search engine is different
• Assign weight to keyword position
• Produce the results list in rank order
• There is a lot of junk as well

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Search engines vary

• How often is it updated?
• (FULL TEXT) Key word in Title of Homepage?
• Some search engines only record home pages
• Some search engines also search the LINKS!
• For speed Use a multiple search Engine

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Broadening a full text search

• Keywords are important
• The use of synonyms (thesaurus)
• The use of Boolean system OR
• Use of Truncates as Walk (for walkers,
  walkabout, walking)
• receive too many HITS

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Broadening a search

• Example

Keyword Results Caving 926 Cave
exploration 44 cave Explor
88 Caving OR cave ex 977
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Narrowing a FULL TEXT search

• Use very specific terms
• Use Boolean AND between words
• Request keyword in title
• Add another concept (such country or date)
• each search engine has an advanced feature
• Use the online HELP

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Narrowing a FULL TEXT search

• Example

Keyword Results biotech research
300,000 biotech research
3,000 Title biotech and Titleresearch
100 Title biotech research AND Europe 3
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Multiple Search Engines

• Http//www.dogpile.com
• Uses 15 independent search engines
• http//www.search.com
• Access to 470 databases
• http//www.webtaxi.com
• 12 most popular and Access to supersearch

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People Directories

• No single listing of emails
• Yellow pages/whitepages
• Universities in Australia eg. Http//staff.connect
  .com.au/mrp/phone.html
• Others such as Http//www.four11.com

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Educational sites

• Some Examples are DETE is at Http//www.nexus.ed
  u.au
• Discovery learning in Canada is at
  Http//www.bc.sympatico.ca/learning/
• The Aussie school house is at http//www.Ash.org.a
  u
• NASA is at http//www.nasa.gov

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Searching the Internet
Prepared by Andrew Barr