While subject directories organize Web sites according to subject categories, Web search engines (such as AskJeeves, Google or AltaVista) are search tools that allow users to search for any word in almost any site on the Web. Search engines should be used when you have a focused research question in mind. They're not recommended for finding sites on broader subjects, such as "astronomy" or "history." As already mentioned, subject directories should be used to find sites on such general subjects. Therefore, one effective strategy for Internet research would be to use a Web subject directory as part of your preliminary topic exploration. Then, once you have a focused topic in mind and are ready to search for specific information, it would be appropriate to use a Web search engine.
Web sites included in search engines are not selected, organized or previewed by humans. Instead, their collection of Web sites are created entirely by computer programs called spiders (also known as robots) that continuously scan the Internet looking for sites to add to the index.
Since search engines' indexes of Web sites are huge and have no subject organization at all, it is very important to think carefully about what search words to use and be aware of the various search features available before performing a search. Always look for the "Search Help," "Search Tips," or other pages that explain the features of the particular search engine you are using. To use search engines effectively, it is usually best to either have very precise search words, or to combine several search words related to a search topic.
FEATURES OF WEB SEARCH ENGINES
AND: many Web search engines use the + sign (often called the "require" sign) in front of words that must be included in the search results. For example, + immigration +economy is often used instead of immigration AND economy. Some Web search engines that do use AND and OR require that these Boolean connectors be capitalized. (Therefore, it's a good idea to always capitalize these connectors if you use them.) Some search engines, such as Google, assume that a typed space = AND. For example, immigration economy is often the same as immigration AND economy.
OR: many Web search engines assume that a typed space = OR. For example, economy business is often the same as economy OR business.
Phrases (consecutive search words): quotation marks (" ") must be placed around phrases in most search engines. For example: "illegal immigration" can be entered to find those two words next to each other as a phrase.
Truncation: only some Web search engines allow truncation. Those that do usually use * for truncation. For example, econom* finds: economy, economic, economics, economist, etc.
Search sets: Web search engines generally do not create sets for search results. Instead they allow the use of parentheses (as in algebraic equations) to designate which logical operators are to be carried out first. For example, in the following search:
("illegal immigra*" OR "undocumented workers") AND econom*
A search engine would first search for: "illegal immigra*" OR "undocumented workers" and the results of these ORed terms would then be ANDed with econom*.
"Relevance ranking": a programming method that attempts to rank search results based on various factors. Different search engines use different ranking systems. Documents returned from a search can be ranked on such factors as:
of search words in document
Finding key words on a Web page: When you view lengthy Web pages, it is sometimes hard to see where your search terms are located. You can find exactly where a specific word is located on the page by using the Find in Page command on the Netscape "Edit" pull-down menu.
Recommended Web search engines:
Adapted from: Skyline College, LSCI 100: Introduction to Information Resources.