Search engine is one of the most important tools for finding information from worldwide web. Some understanding on how they work can help you get the maximum out of them.

Please note, our earlier series on Search Engines was on how to get top placement in search engine result. This series on search engine is from information retrieval point of view.

You will find four main types of retrieval tools in the WWW:

•  Directory type search engine
• Spider based search engines
• Meta Search Engines
• Databases driven retrieval An understanding of how each of them work is crucial for retrieving right information at right time.

Directory Type Search Engine

This type of search engines list websites under categories (sometimes called category database). They have large number of categories to fit all kinds of webpages. Largely managed by human beings, the two outstanding features of any directory are accuracy and selectivity.

Directories are extremely selective about webpages to be accepted. A directory will not list your URL and will never become aware of your site unless you register with them. They do not make use of spiders or robots that crawl the web looking for new sites.

As a result - you will find only a handful of sites under each category.

This selective approach makes sure that search in a directory produces only a few relevant webpages unlike spider based ones that list thousands. T

he most famous directory type search engine is Yahoo!

Few Facts About Directory Type Search Engine

1. Search result is usually highly accurate and selective. You can easily go through all websites listed in a category. Often, starting point in a long and exploratory search.
2. The results are usually listed in alphabetical order rather than on degree of relevance.
3. An understanding of categories can help you quickly zero-in to required websites. Presence or absence of keyword is not critical in category search.
4. If you are looking for a very specific subject, Directories may not be the right retrieval tool.
5. If you are submitting your site to a directory, decide on right category and description first. Prepare to wait for weeks before your website gets listed. Do not get disheartened if your site is not accepted - keep trying
6. Successful listing in a directory like Yahoo! will certainly lead to more traffic on your site.
7. Using a directory-cum-search engine like the Yahoo! Google gets you best of both worlds !

We shall discuss other retrieval tools in forthcoming issues.