Boolean Operators

Advanced Search uses boolean search operators (AND; OR; NOT) between sections to narrow or expand your search.

Boolean operators are used to connect and define the relationship between your search terms in eHRAF. You will find radio buttons for the operators AND, OR and NOT separating the different sections of the Advanced Search form.

Be sure to carefully set the boolean operators between each section of the search form in Advanced Search. Always double-check the radio buttons before submitting your search. Selecting the incorrect operator for your search can severely limit or expand your results.

In brief, choosing AND will narrow your search because it requires that all of the terms entered are present at the same time in the search results. OR will expand the results to include matches for any of the terms entered. NOT will restrict certain terms from your search.

Remember that Advanced Search searches against the full-text contents of eHRAF, but results are matched at the paragraph level, not by whole pages or chapters. Therefore, using the AND operator will mean that if two terms appear on the same page of a document, but not in the same paragraph, it will not show up in your search results. To expand the results, choose OR instead.

Keywords and Boolean Operators

When entering more than one search term:

  • Use OR to require that only one term needs to be present in the text of a paragraph.

For example, use it for related or “sibling” terms (e.g. dog* canis* canine*).

  • Use AND to require that both terms be present in the text of a paragraph.

For example, use it for unrelated or “paired” terms (e.g. cook* herb*).

AND can limit your results for two terms, and greatly limit three or more terms. When using the AND operator, the more keywords or subject codes you enter, the fewer results are likely to be found.

  • Use NOT to restrict certain keywords from your search results.

For example, NOT "herb*" to exclude reference to herbs when looking for information about food or cooking.