Understanding Search Engines

Learning Outcomes  Search Engines  Search Techniques 
Evaluating Web Pages  Citing Web Resources

What is a Search Engine?

A search engine is a program that searches the World Wide Web when a user enters a keyword for phrase and presses the Search button. The engine performs a search then returns a list of documents that contain the keyword(s). A results page with a list of linked pages along with a brief description of the information displays in ranked order according to relevance. This allows the user to quickly review the content and to follow the links that seem to be most related to the research question.

Without search engines, it would be nearly impossible to locate information on the Web and certainly there would be no organized way of finding information.

Types of Search Engines

Search engines can be categorized in a number of ways. The "SearchEngineWatch" site has categorized them as:

• Major Search Engines and Directories

• Metacrawlers and Metasearch Engines

• Specialized search engines

In addition, some Web sites have their own site search engines usually displayed as a search text box on the home page. You can see an example at the Nashville State Community College home page.

Major Search Engines and Directories

Follow the "Major Search Engine" link to see a list of some of the more popular search engines and directories. Search engines use "crawler" or "spider" software to search the Web and are often referred to as crawler-based engines. Directories are categorized by subject and are generally created by human intervention.

Some of the more popular search engines and directories are listed in Tables 1 and 2.

Metacrawlers and Metasearch Engines

Rather than doing the same search several times, you can use a metasearch engine to compile a search from several search engines. Some do a better job than others by not returning duplicate listings. Dogpile, Excite, WebCrawler, and MetaCrawler are some of the major metasearch engines. Follow the "Search Engine Watch" link to see a more comprehensive list.

Specialized Search Engines

There are many specialized search engines that target only specific types of information such as news, travel, shopping, computers, and mailing lists. Go to the Specialty Search Engine page to see an extensive list of specialized search engines. Follow the links from the Government Search, Invisible Web, Legal Search, and Medical Search to understand the extent of using specialized search engines.

For scholarly materials, try the following search engines. Each of the sites provides information about the search tool including peer review.

How Do Search Engines Search?

Search engines use different technologies for gathering and ranking the relevance of search results. The same keywords entered in each of the search engines will return different results. Each has its own set of rules for conducting searches.

Likewise, metasearch engines present search results in different ways. For example, Dogpile presents results grouped by their original source, but MetaCrawler presents the results based on relevancy. It is important to become familiar with a variety of search engines so you will be able to select the best engine for the type of research you need to do.

Select the Right Tool

Selecting a Tool for Your Research created by the University Libraries, University of Albany, offers guidelines to help a beginner or advanced user choose the best search engines based on the type of research question. It is recommended that you print the guidelines handout and use it as a resource for choosing search tools for class assignments.

Choosing a Search Engine or Directory created by the University Libraries, University of Albany, offers suggestions for choosing search engines based on the type of material you need to locate.

Activity

Click on the links from each of the tables and look at the "About" or "Help" information to gain a better understanding of search tools.