Search Tool Characteristics

Because search tools are constantly changing, we will not attempt to explain each in detail. Instead, we focus on the characteristics of directories, indexes, and metasearch engines.

Directories

Directories are search tools maintained by humans. The people who maintain directories usually take submissions or use automated tools to find new pages on the Web. The pages are then summarized and placed into a category.

In many ways, directories are organized like a library catalog with subject headings and sub-headings. Some directories will also review and rate the pages they catalog. To use a directory, you browse through the subject headings to find what you're looking for. Many directories also make it possible to search the database by keywords.

One of the first search tools that fell into this category was Yahoo (http://www.yahoo.com). Created in 1994, it is one of the oldest and most popular directories on the Web.

Indexes

Another category of search tools are indexes. The main characteristic that distinguishes indexes from directories is how their database information is gathered and organized. An index is generated automatically by using small computer programs called robots, spiders, or crawlers. These programs continuously visit web pages, record information they find, and add it to the database. Search tools developed this way are often called "search engines."

Because they are generated automatically, indexes can become quite large. This size makes it difficult for indexed search engines to provide the descriptive summaries and organized categories for all their web pages. Instead, the search engine will likely display the first few lines of the actual web page and group more popular web pages into categories. Keyword searching remains the primary means for finding information in indexes.

Metasearch Engines

Tired of keeping track of which search engine to use? You may want to use a metasearch engine. Metasearch engines act as a go-between between yourself and individual search engines. Once you type in your search terms, the metasearch engine will send your query to each search engine it uses. The results of your search are then organized and ranked according to their relevance. Because they search many different search engines, metasearch engines are limited in the complexity of search queries they can process.

Specialized Resources

Indexes and directories are popular search tools on the Web because they cover a wide range of topics. The Web is also home to several types of specialized search resources that may help you find information. The Internet Scout Project (http://www.scout.cs.wisc.edu/) calls these specialized resources "subject guides," and "specialized directories." The strength of these resources is that they are developed by experts or provide access to data that would otherwise be difficult to find.