Benjamin Baron
Spring 2009

SLIS 5200 TXWIC

Concept Briefing

Search Operators

Abstract

Search operators serve search systems users by controlling the logical relationships between search terms and thereby control the scope of search criteria. Search operators allow users to tailor their search criteria and receive results that appropriately relate to their search goals. This briefing addresses the purpose and use of search operators, describes common search operators, and considers the usefulness and limitations of search operators in the context of current search behavior. This report also discusses the results of recent studies that analyze the effectiveness of search operators as related to user recall and user search behavior. Examples are provided to illustrate methods of using search operators to limit and target search criteria.

Baron / TXWIC / p. 1

Introduction

This briefing seeks to educate readers on the subject of search operators by: (1) addressing the purpose and use of search operators, (2) addressing basic types of search operators, and (3) considering the usefulness and limitations of search operators in the context of current search behavior.

Definition

Search operators are logical switches in information retrieval (IR) systems that searchers use to limit or broaden the scope of or control the final results of a query. Search operators exist in many forms and display a variety of syntax based on system design. Search operators broaden, narrow, or eliminate search results. Users control the logical relationships between terms by using search operators (Boolean Operators, 2009).

Purpose and implications

Purpose and use of search operators

Users include one or more search operators in a query to adjust the outcome of the search. Rather than searching by subject terms alone, users utilize search operators to control the subject terms and affect the results of searches, thereby reducing the number of results unrelated to the initial search criteria. Both explicit and assumed use of search operators exists in current search systems (Clyde, 2000).

Types of search operators

Depending on the type of IR system used, different search operators exist. While Boolean operators are common to most systems, there are some exceptions. Boolean operators are basic operators (AND, OR, NOT) that follow Boolean logic. These types of operators are applied to search terms in order to limit the scope or control the results of a query. Online search engines often possess special search operator languages, and in some cases, Boolean operators are assumed, making the need for explicit entry of the operator unnecessary (Bell, 2007, p. 23).

In some cases search operations utilize brackets or parenthesis to connect related terms, allowing users to create algebraic search strings. Operators used in this manner lead to the retrieval of very specific results. Proximity searching uses special operators like NEAR, WITHIN “X”, BEFORE, and AFTER. These operators allow users to search for words within a phrase. Proximity search operators tailor searches by

The usefulness and limitations of search operators

Search operators are effective in serving users that search specific, limited query terms; however, search operators are not effective in serving users who display browsing behavior (Taylor, 2004), eliminating a large segment of searchers and searches from consideration. Moreover, the use of search operators appears to be even more confined to a small segment of the researching public. A study on query term and operator usage by Lucas and Topi (2002) found that, “…the majority of searchers enter term-based queries containing approximately two terms and rarely use operators,” and that, “less than 5%used any Boolean operators, and those that did often contained mistakes” (p. 95).

Another limitation in using search operators is that users must understand how to use the system syntax in order to conduct a successful search. If the system is used occasionally user problems associated with adjusting to system may limit search results. Yuan (1997) addresses this limitation saying, “…users currently have to understand and adapt to the system they want to use. They learn to use the system and adjust to it by practice… Because they tend to learn limited information initially and use the system only occasionally, the learning and adjusting can be a fairly long process for end users.” (p. 218)

Questions exist surrounding the effectiveness of operators within modern search systems. A 2004 study of Internet search engine operator usage indicates that the inclusion of search operators in a search string does not result in significantly greater recall (Jansen, 2004, Discussion ¶ 1), and found that the likelihood of error increases with the use of advanced search operators (Discussion ¶ 2). As public search systems become increasingly easier to use the need for advanced search operators is in question.

Examples

Example 1: Using the AND and OR operators in a search phrase.

The AND operator narrows a search by returning results containing all of the connected terms. The OR operator A user searches for “Napoleon AND (canon OR musket). All returned search results contain the term “Napoleon” and contain either or both of search terms “canon” and “musket”.

Example 2: Using the NOT operator in a search phrase.

The NOT operator eliminates a search terms and returns results that do not contain a search term. A user searches for “Napoleon” NOT “canon”. Returned results contain the term “Napoleon” but do not contain the term “canon”.

Example 3: Using the NEAR operator in a search phrase.

The NEAR operator searches for both of the search terms within a phrase. The NEAR operator is the same as WITHIN 10 (Boolean Operators, 2009). A user searches for “Napoleon” NEAR “canon”. Returned results contain the terms “Napoleon” and “canon” when the terms appear within 10 words of each other.

Conclusion

Search operators allow system users to tailor their searches by manipulating the way results are returned, using basic logical relationships to narrow, broaden, or eliminate search criteria. While search operators are powerful tools for controlling search criteria, they are often overlooked and unused by a large portion of the searching public, as they do not allow for browsing behavior. There are also questions as to the current effectiveness of manually entered search operatorsbecause many modern search platforms either assume the use of search operators and/or users do not take the time to learn and use a system’s search operators to their advantage.

References

Bell, S. (2007, September). Tools Every Searcher Should Know and Use. Online, 31(5), 22-27. Retrieved April 6, 2009, from Library, Information Science & Technology Abstracts with Full Text database.

Boolean Operators. (2009). Retrieved April 9, 2009, from CSA:

Clyde, A. (2000, April). Search Engines. Teacher Librarian, 27(4), 22. Retrieved April 6, 2009, from Library, Information Science & Technology Abstracts with Full Text database.

Jansen, B. (2000, October). The effect of query complexity on Web searching results. Information Research, 6(1).Retrieved April 6, 2009, from Library, Information Science & Technology Abstracts with Full Text database.

Lucas, W., & Topi, H. (2002, January 15). Form and Function: The Impact of Query Term and Operator Usage on Web Search Results. Journal of the American Society for Information Science & Technology, 53(2), 95-108.Retrieved April 6, 2009, from Library, Information Science & Technology Abstracts with Full Text database.

Taylor, A. G. (2004). The organization of information (2nd ed.). Westport, CT: Libraries Unlimited.

Yuan, W. (1997, March). End-User Searching Behavior in Information Retrieval: A Longitudinal Study. Journal of the American Society for Information Science, 48(3), 218-234.Retrieved April 6, 2009, from Library, Information Science & Technology Abstracts with Full Text database.