Research and Course Guides: American History 110: Skill Unit 4

Bolean Logic

Use Boolean Logic (AND, OR, NOT) to combine search concepts.

TOO FEW hits: OR to add synonyms; individual key words, NOT whole phrases; drop concept(s) with AND; truncate; consider other databases.

TOO MANY hits: AND another concept into search; use other available limiters in the database.

Truncation symbols (?, *, !, +) will provide variant spelling after the root word.

A wildcard (?, *) is a character that may be used in a search term to represent one or more other characters.

Do an advanced search and take advantage of the fields provided.

Use the subject headings/descriptors to find additional citations on your topic. If that does not work, use the keyword search.

You can also use limits (e.g., publication year, language, words in the title, etc.) to narrow your retrieval.

Set up an auto alert/RSS feed to monitor the research.

Skill Unit 4

Boolean logic is a system of showing relationships between sets by using the words AND, OR, and NOT. (The term Boolean comes from the name of the man who invented this system, George Boole.) Boolean logic is recognized by many electronic searching tools as a way of defining a search string.

Boolean searching is an important tool that can be used when searching catalogs, indexes, online databases, and the web.

Here are some examples of boolean search strings:

mushing AND racing
caribou OR reindeer
fisheries NOT Alaska

Boolean logic is a bit more confusing than it seems. Sets get smaller the more "AND" is used, and larger the more "OR" is used. Although you might think "AND" would add more hits to a set, what it has actually added is limitations. The term "OR" adds possible options. A good way to illustrate how boolean logic works is through a Venn diagram. The circles in a Venn diagram illustrate different sets and the shaded areas show how the boolean terms form relationships between the sets.