Boolean Searching

How Search Engines Understand Boolean Rules

The search engines robots recognize three ways of using Boolean operators:

• fully Boolean
  where the operators AND, OR and NOT are entered in capitals
• implied Boolean
  where the plus sign (+) represents AND, the minus sign (-) represents NOT,
  and no sign at all is automatically taken by the robot as an OR relation
• a menu expressing the Boolean relation in brief sentences like:
  + all of these words (=AND)
  + any of these words (=OR)
  + must not contain (=NOT)

In order to get the most relevant hits at the top of the list, various techniques are applied that may be very different from one another. Each search robot has its own system of:

• collecting sites and adding to the database;
• organizing sites in the database;
• searching the database;
• establishing relevance
• presenting information

A small difference in one of these four elements will affect the results of the search action. This is one of the reasons why results differ for each robot when you are using the same terms as search options. This is also why you should always consult more than one search robot.

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This file prepared and presented as an aid to help students understand the web.  Send questions or comments to Royce Shook