Syntax – Boolean

In the early days of online databases, searchers learned to use the logical connectors AND, OR, and NOT (or their equivalents) to construct queries that quite precisely described the information to be retrieved. These logical connectors have their origin in Boolean algebra for the analysis of the relationship of sets – from whence the name Boolean. (Boolean algebra was named after George Boole, a British mathematician.) We can apply the same thinking in constructing queries on web search engines, although the query construction is a bit different.

Conceptually, we may wish to:

  • Look for pages that consider Concept A AND Concept B. For example, we might want information on the nutritional value of hot dogs. There are two concepts: nutrition AND hot dogs.
  • Expand a search by considering alternatives: perhaps the nutritional value of “hot dogs” OR frankfurters.
  • Exclude an aspect that might muddy the waters: you might not want beef dogs. nutrition AND (“hot dogs” OR frankfurters) NOT beef

The following table illustrates the three Boolean operators.

Boolean Operators Venn Diagram Tips on use
AND used between two words or phrases means that the information you want must include both.
AND
Web search engines assume AND – Don’t waste time entering it.
OR used between two words or phrases means either word will satisfy your query. Use OR as a way to list synonyms, or capture variant spellings like labour OR labor.
OR
Most valuable operator. Must be in upper case at all search engines.
NOT used between two words or phrases means you want to exclude pages that have this word or phrase in them. dogs AND cats but NOT breeders. NOT Bing will recognize NOT, but the standard is to use the minus sign.
NEAR asks for words to be within a certain distance of each other. At Bing you can use near:n where n=number of words. Eg drought near:3 australia Google has AROUND(n) which does the same thing.  However since search engines rank results so well this has limited use.

Boolean Exercise

Boolean is most useful when we need to look for like things such as synonyms or (sometimes) alternate spellings. In this search we are interested in learning more about the history of Inuit people in North America – or Eskimos as they are still known in some areas.

  1. Bing   history  AND (inuit OR eskimo) AND “north america”. The AND is optional – leaving it out will produce the same number of results.
  2. Google  history (inuit OR eskimo) “north america”. You can also use the pipe | instead of the word OR — inuit | eskimo

Exercise

Use Google to look for online courses about writing. Such courses might be called a writing course or writing class. You’ll need online and perhaps e-learning. Virtual is used sometimes as a term. Add other words later to indicate the type of writing: humour, business, technical, fiction etc. Run two or three queries to see what works best.

Check your search construction against the syntax answer page.

Next

Google’s synonym operator.