Once you have developed a research question that has multiple concepts, you're ready develop a search strategy so you can carry out effective searches in computer databases that will find the best information for your topic. Let's continue with the research question, "What is the effect of illegal immigration on the U.S. economy?"

Dividing a Research Question into Concepts

The first step in the process of developing a search strategy for a topic is to analyze the research question (or research topic) and break it down into main ideas or concepts such as "illegal immigration" and "U.S." and "economy" in the previous example. A typical research question should be able to be divided into two or three (or occasionally four) concepts. If you can only identify one concept, the topic is probably too general. More than three or four concepts is likely to be too specific.

Breaking a research question (or research topic) into appropriate concepts can sometimes be a tricky process. A topic can often be divided into various different combinations of concepts. Each concept should be stated as precisely and succinctly as possible and words that describe the relationship between concepts should not be included. Only the most significant words from the research question (or topic statement) are usually included as terms for one of the concepts. Words that are not essential in defining a concept (such as "what" and "effect" in our example) should not be included as terms.

Finding Synonymous or Related Terms for Each Concept

Once the topic has been broken into basic concepts, as many search terms as possible should be listed for each concept. Any terms that are synonymous or closely related to a concept should be included. If we take the concept, illegal immigration, from our search example, we might list the following additional related terms for that concept: illegal immigrants, illegal aliens or undocumented workers. For the concept, economy, we could also list economics. For the concept, U.S., United States and American should also probably be included.

Using a Search Worksheet

It is very useful to organize the various search terms for each concept in a research question by using a "Search Worksheet" as is shown below.


Research Question (or Topic):

What is the effect of illegal immigration on the U.S. economy?

Search Terms
illegal immigration
illegal aliens
undocumented workers






United States



Boolean Logic

Most online databases allow users to create various relationships between search terms which can define a topic very precisely. These relationships are created by inserting special words, referred to as "logical operators", between the search terms. There are two logical operators most commonly used by most electronic databases. The operators are: OR and AND. The use of these operators is called Boolean Logic (named after George Boole, a 19th-century British mathematician.)

The OR operator is used between terms with the same or similar meaning--between different terms for the same concept. Placing an OR between two search terms instructs the computer to search for all of the records containing either the first term OR the second term. In this way the OR operator expands a search. It is common to use "OR" between each of the terms related to one concept. For example, if you type: "illegal immigration OR illegal aliens OR undocumented workers", the computer would retrieve all the records that are related to any of those terms--either "illegal immigration" or "illegal aliens" or "undocumented workers".

The AND operator is used between different concepts. Placing an AND between two terms instructs the computer to search for all of the the records containing both the first AND the second term. The AND operator narrows a search. "AND" is typically used between different concepts. For example, if you type: "illegal immigration AND economy," the computer would search for all the records dealing with both "illegal immigration" and "economy."

In many databases, such as the InfoTrac OneFile & Gale Resource Center databases, an Advanced search mode allows you to enter all of the search terms for all of your concepts in a single search. Separate entry boxes are provided for each concept with a choice of Boolean operators (e.g. AND or OR) available between each of the entry boxes.

Using the Advanced Search Mode on Skyline Library Periodical Databases describes how to carry out a search with multiple concepts on InfoTrac & Gale Resource Center databases (including the History Resource Center, Literature Resource Center, Business & Company Resource Center, and the Health and Wellness Resource Center databases).

When you actually look at the records in the result list for a search, you may find that your search needs some further refining. The number of records retrieved by a search are often referred to as "hits". Records retrieved by a search that are not relevant to the topic are sometimes called "false hits". One of your concepts may have limited your search too much, for example, or you may need to limit your search even further with an additional concept. Check the subject headings assigned to any records that seem particularly useful. You might find additional search terms to improve your search. Each time you do a search on a topic, it is important to analyze your results in order to try to find ways to further refine your search.

Truncation and "Wildcards"

It is common to find that several search terms identified for a single concept may begin with the same root. For example, for the concept economy, you may also want to include economic or economics or economist. Instead of listing all of these terms separately, many databases allow a search procedure called truncation. The truncation feature lets you use a special symbol to search for any words beginning with a particular root. The most common truncation symbol used by many databases is the asterisk (*), but some databases use the question mark (?), or the exclamation point (!). In our search example, we could use truncation to search for "economy" or "economic" or "economics" or "economist", by simply entering "econom*" in the InfoTrac or Gale databases. It is important to be careful, however, when using truncation, because if you truncate after too short of a stem, you might retrieve words that you don't want. If you used eco* instead of econom*, for example, you would also retrieve records with the words ecology or ecosystem.

In addition to the use of truncation for words with same root but different endings, some databases allow the use of a special symbol, often called a wildcard, in the middle of a word to search for spelling variations such as adviser or advisor. The "wildcard" symbol would be used in place of the letter that may vary, e.g. advis?r would find either adviser or advisor.

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last revised: 10-25-05 by Eric Brenner, Skyline College, San Bruno, CA

These materials may be used for educational purposes if you inform and credit the author and cite the source as: LSCI 106 Online Research. All commercial rights are reserved. To contact the author, send comments or suggestions to: Eric Brenner at