LESSON - SEARCH ENGINES

What is a search engine?

Imagine our huge shopping mall with layers and layers of stores. It's pretty intimidating and you don't know which sections have the stores you want. That's the Web. Now imagine that you are at the information desk and you can ask the attendant to bring back information on whatever interests you. This attendant is a search engine. You just have to give this person the right instructions.

Where do I go to search?

There are several different types of search engines and literally millions of places to look for what you want. Before you choose which site to visit, you should ask yourself, "What am I looking for?" Among other things, you could be looking for:

  Information
  People
  Shareware
  Music or Pictures
  Something to Buy

Some sites search the entire Internet, but some sites have internal search engines that only look at their own pages. Usually when people use the term "search engine," they are referring to popular sites like AltaVista, Northerlight, Ask Jeeves, Google or Excite.

Search Engines vs. Directories

There are two fundamentally different types of search services available on the Web, and it's important to understand the difference between them.  Search engines are actually full-text indexes of Web pages.  They're similar to telephone white pages, which contain nothing more than lots of names with phone numbers.

Search engines such as AltaVista (www.altavista.com), HotBot (www.hotbot.com) and Infoseek (infoseek.go.com) use automated software called Web crawlers or spiders. These programs move from Web site to Web site, logging each site title, URL, and at least some of its text content. The object is to hit millions of Web sites and to stay as current with them as possible. The result is a long list of Web sites placed in a database, which users search by typing in a keyword or phrase.. When you search an index, you're trying to coax it to find a good match between the keywords you type in and all of the words contained in the index. In essence, you're relying on a computer to essentially do simple pattern matching between your query words and the words in the index.

Directories, on the other hand, are collections of links to Web sites compiled by people, not software robots. Directories are similar to telephone yellow pages, because they are organized by category or topic, and often contain more information than bare-bones white pages listings. Also, as in the yellow pages, some sites can have different types of advertising to make them stand out more.

Directories have the advantage over search engines in that they can be very precise in how they categorize pages. Many directories annotate their links with descriptions or comments, so you can get an idea of what a site is about before clicking through. About.com (home.about.com), LookSmart (www.looksmart.com) and Yahoo! (www.yahoo.com) are examples of directories.

Here is why your web site will not be submitted to Yahoo.  It is easy to let other search engines know that you exist and eventually, they will get around to "spidering" our site.  Yahoo, on the other hand, requires a lot of criteria around the submission and it becomes too difficult to do.

Which Is Better?

The key advantage of an index is size—indexes typically have information on millions and millions of Web pages. This size, unfortunately, can also be a problem for common subjects. There's often no way to determine the quality of a link in a result list you get from a search engine's index.

The advantage of a directory is that the links will almost always be of much higher quality, but the scope of the results necessarily will be much smaller than that returned by an index, so you might miss something a search engine might have found. Another key advantage of directories is that they are organized in a hierarchical format, which lets you "drill down" through subject trees, "browsing" for links in much the same way you browse for books through stacks in a library.

So the answer is that neither is "better"—in general, a search engine is best when you want lots of results, and a directory is better when you want focused results.