Search Engines - Internet Technologies

What are Search Engines?

Search Engine helps in locating information on WWW. It refers to the database of internet resources of web pages, images etc.

By giving a keyword, user can find any information over internet. Then the engine searches for relevant information in its database and returns it to the user.

 Search Engine Components

Search Engine Components

The three basic components of a search engine are below.

  • Web Crawler
  • Database
  • Search Interfaces

Web crawler

Known as spider or bots as it traverses the web to gather the information.


Database stores the information on the web consisting huge web resources.

Search Interfaces

Between user and the database, this component acts as an interface. User search through the database using this interface.

Search Engine Working

  • Search Engine works using Web crawler, database and the search interface components. Boolean expression AND, OR, NOT are used to restrict and widen the results of a search. Below are the steps a search engine performs:
  • Search engine search the predefined database using the index of the keyword instead of searching the web directly.
  • Web crawler is the software used to search for the information in the database.
  • When the web page is found, the search engine displays the relevant page as a result. These web pages include title, size of text, several sentences etc.
  • Every search engine has its own search criteria. Information retrieved is ranked upon number of factors such as frequency of keywords, relevancy of information, links etc.
  • Users can click on any of the search results to open it.


Below diagram depicts the Search engine architecture.

  • Content collection and refinement.
  • Search core
  • User and application interfaces


Search Engine Processing

Indexing Process

Indexing process contains the below three tasks:

  • Text acquisition
  • Text transformation
  • Index creation


Identification and storing documents for indexing is done.


Document is transformed into index terms or features.


The index created by transforming text is added to the data structures for fast searching.

Query Process

Query process contains below three tasks:

  • User interaction
  • Ranking
  • Evaluation


Creation and refinement of user query and results display is supported.


Ranked list of documents are created by using query and indexes.


Evaluation is done offline and it monitors and measures the effectiveness and efficiency.


Below are the search engines available today:

Search Engine Description
Google It was originally calledBackRub.It is the most popular search engine globally.
Bing It was launched in 2009 byMicrosoft.It is the latest web-based search engine that also delivers Yahoo’s results.
Ask It was launched in 1996 and was originally known asAsk Jeeves.It includes support for match, dictionary, and conversation question.
AltaVista It was launched byDigital Equipment Corporationin 1995. Since 2003, it is powered by Yahoo technology.
AOL.Search It is powered by Google.
LYCOS It is top 5 internet portal and 13th largest online property according to Media Matrix.
Alexa It is subsidiary of Amazon and used for providing website traffic information.

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