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Module 2:
About AND |
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©2019 by Chris Niemeyer, University of Missouri-St. Louis.
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Module 2:
About AND |
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©2019 by Chris Niemeyer, University of Missouri-St. Louis.
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We mentioned in the previous module that library databases interpret the three words below in specific ways.
These words form three of the "Boolean operators" which are used in symbolic logic systems. Screen2 AND OR NOT |
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Of these three Boolean opeators, the word AND is the one most users will have to deal with.
Screen3 AND OR NOT |
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As an example of what we mean, look at the query below from the previous module.
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cell phones accidents
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Despite its simplicity, this keyword search could be a failure in some library databases.
Why? Because some library databases could treat three keywords together as a single term, such as gross domestic product or systolic blood pressure. Screen5
cell phones accidents
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It is unlikely that any record would contain a grammatically incorrect term like cell phones accidents.
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cell phones accidents
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But rephrasing the search with AND makes it comprehensible to a library database.
Using AND in this way breaks the search down into its two major concepts of cell phones and accidents. Screen7
cell phones
accidents
AND
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Additionally, AND ensures that EVERY record MUST contain both concepts.
The concepts can appear in any order in a record, but they both MUST be present in every single record. Screen8
cell phones AND accidents
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If the below search results in 2,000,000 "hits"
(i.e., records), then each and every one of the
2,000,000 MUST have cell phones and accidents!
All because of AND! Screen9
cell phones AND accidents
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In contrast, Web search engines often retrieve hits according to "relevance", such that subsequent hits may or may not contain all search terms.
This is not a bad approach, just one that makes it different from what a library database does with AND. Screen10
cell phones AND accidents
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Library databases use AND so much that it is common to see the term built into search screens as the principal (default) pull-down menu option.
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cell phones
AND
accidents
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The expanded search below could be written on a single search line as:
cell phones AND accidents AND laws Screen12
cell phones
AND
AND
accidents
laws
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Since all three terms are separated with AND, every record MUST contain these three terms somewhere.
cell phones AND accidents AND laws Screen13
cell phones
AND
AND
accidents
laws
Module finished!
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