Web Search Tools > 3: Search for Specific Information

3A: About Web Indexes

Sometimes browsing isn't the best approach, particularly if you need rather specific information. In a library, you would examine the index in the back of a book to see whether it contains information on a specific topic. On the Web, when you know what you are looking for, use a Web Index (also called a "search engine") to locate it. Using a Web Index is like searching within the indexes of all the books contained in the world's largest libraries at once.

- - - Characteristics of Web Indexes:

1. Size: They are huge. For example, Google indexes billions of Web pages.

2. Built by robots: They are built and maintained by a software program called a robot, spider or crawler. This program roams the Web, collects information from Web pages, and stores this information in a database called an "index."

3. Contain all words on pages: The Index contains all of the words on each Web page that is included in it. This allows you to find rather obscure information, but also makes it harder to get good results for many searches.

4. Not comprehensive: Each index has some unique contents, and no one index covers all of the Web.

3B: Types of Web Indexes

Some examples:

• General -- cover all subjects

  Ask.com
  Bing
  Duck Duck Go
  Google
  Yahoo! Search

   

• Topical -- cover one area in depth

  Business.com
  search.USA.gov
  Political Information.com
  Scirus (science)
  Truveo Video Search
  

  Research Tip

  When available, use a topical (or "vertical") search tool.

  "If you want to drive a nail into a piece of wood, you reach for a hammer, rather than a screwdriver. Use the right tool, and you'll get the right results. The same is true with search engines ... Like a Swiss Army Knife, general purpose search engines often can do many different jobs. Nevertheless, your results might be better if you turn to a vertical tool."

  Danny Sullivan, editor, SearchEngineWatch.com

  3C: More Features of Web Indexes

  - - - Companion Directories and Databases

  Many Web Indexes have evolved into "one stop shopping" sites. They also offer access to a Web Directory and some specialized databases, such as images, current news stories, people, etc.

  In Yahoo! (shown in the illustration below), you can jump into the Directory simply by selecting that resource at the top of your search results.

  

  - - - Ranking Search Results

  All Web Indexes try to rank your search results and list the MOST relevant results first. Sometimes a relevance percentage is also displayed next to each result. Higher percentages indicate more relevant results.

  How does the Index determine which pages are most relevant?

  • Algorithms: These mathematical formulas take into account how often and where your search words occur. If search words are found in a Web page's title or headers, it is more likely to be relevant.

  • Popularity: Sites which have also been selected for inclusion in Web Directories, linked to by other "high quality" sites, or viewed most often by others searching for the same words are considered most likely to be useful.

  - - - Clustering Search Results

  Clustering means that only one page from a Web site will be listed in the top search results. Some Indexes automatically cluster your results so that you will see a greater variety of pages that match your search words, not just many from one site.

  See a Movie

  Watch Google Basics or select from this list of movies about search engines. [opens in new window]

  3D: Specialized Databases

  Using a specialized database is like finding a good reference book in the library that covers your research topic in detail. Use a specialized database to locate specific, factual information.

  For example, the Cinema Treasures: Theatre Guide is a database about classic movie theatres. It's the quickest way to find facts about a particular theatre.

  Here are a few examples of specialized databases available on the Web:

  Bartleby.com: Great Books Online

  College Navigator

  Internet Movie Database (IMDB)

  MapQuest

  There are many others that will help you find information for research projects. The net.TUTOR tutorial on "Specialized Databases" provides more information about locating and using these handy tools.

  Activity

  Compare search results from different types of Web Indexes. Search for the words: information warfare in:

  • Google (a general Web Index)
  • Google U.S. Government Search (a topical index of government and military sites)

  Browse the first page of results from each index. Is there much overlap?

  [Sites open in a new window.]

  Pop Quiz

  To determine which Web pages are most relevant, search engines may use:   choose one Algorithms Site popularity Both of the above

  Correct answer: [NOTE: Score is not recorded]
  

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