The Internet Book

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The Internet Book
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Chapter 25
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Description Of Functionality

• An automated search service allows one to find
  information that resides on remote computers.

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Browsing Vs. Automated Searching

• The size of the Internet makes it impossible to
  find specific information by searching one
  computer at a time.
• Called Browsing
• The solution is to use an automated search engine.

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A Search Engine Helps Users Get Started

• Automated searching is especially helpful when a
  user first begins to explore a topic.

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A Search Tool Can Help Recover From Loss

• Automated search tools help users recover
  quickly when the location of information is
  lost.

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Automated Searching By Name

• One can search by specific name or content.

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How An Automated Search Service Operates

• Search engines
• gather information
• store it locally
• Servers do not have to search the entire Internet
  when responding to a users request.

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Figure 25.1
Figure 25.1 An illustration of the two-step
process an automated search service uses. (a) A
spider program automatically contacts web sites
and obtains a list of available items. (b) When
someone uses a browser to contact the search
engine, the server consults the database on its
local disk.
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Modern Systems Search Web Page Contents

• Users can assume the search will look for Web
  pages matching the topic specified.

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How A Web Search Appears To A User

• Search services are
• Accessed through a Web site
• Search services
• Require user interaction
• Use forms technology

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Figure 25.2
Figure 25.2 An illustration of how the Web page
for a search service might appear.
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How A Search Engine Returns Results

• The search engine creates a Web page that has a
  link to each found topic.
• Uses cgi technology to create pages dynamically

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Figure 25.3
Figure 25.3 Illustration of the main part of the
users screen after a search engine returns the
results of a search.
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Automated Search Services Use String Matching

• The simplest automated search mechanism is string
  matching.
• The user enters a topic, the search engine finds
  Web pages that contain that topic string.

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String Matching

• Advantages of string matching
• Simplicity
• Disadvantage of string matching
• Lack of semantics
• Inability to tell meaning of word

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Advanced Search Programs

• Some search engines offer multi-key search
  service.
• Group synonyms with a common theme together

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Advanced Services- More Sophisticated Matching

• Some services offer the opportunity to give more
  detailed specifications.
• Use plus sign to denote a required term

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Personalized Search Results

• Search engines keep information about users and
  use the information to select and order search
  results.
• Results in users getting different search results

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How An Automated Content Search Works

• The search service runs a program called a
  spider.
• Explores Web
• Compiles a list of topics
• Stores list on server disk
• This is one way to avoid useless information.

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Searches Are Restricted

• Automated search services search only the
  beginning of each page.
• Use the META tag
• Allows specific keywords that do not appear in
  the browser

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Advertising Pays For Searching

• Web searching appears to be free.
• Uses advertising to generate revenue

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Example of Automated Search Services
Figure 25.4 Examples of automated search services
available on the World Wide Web. Although most
services provide a general index to Web pages, a
few are restricted to specific types of
information.
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Significance Of Automated Web Search

• Automated search engines have become an essential
  part of finding information.
• Growing rapidly on the Internet

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Conclusion

• How do search engines help users find information
  on the Web?

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Glossary

• Personalized Search Results
• Results from a search engine that are
  personalized to the user who makes the request.
  Personalization depends on a history of searches
  and web accesses.

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Glossary

• Wide Area Information Server
• (WAIS) An early automated search service tht
  permitted one to locate documents that contain
  key words or phrases.