Major Search Engines

Search engines work with “robots”, which are indexing full texts (or large parts of it) of internet documents. While doing a search this robot is retrieving data from the indexes. The search system looks for documents with the best resemblance to your search question, and sorts the results based on resemblance. This is called relevance ranking.

Most search engines are easy to use. Using the “best-match” method provides the best results. This method involves typing as many search terms related to your topic as possible.

Most of the search engines nowadays are searching default on ‘all of the terms’.

We have selected the following search engines to support you in your searches:

Google, Yahoo! and Teoma.

• See SearchEngineWatch for the latest developments on these and other search engines
• For tips on how to search with search engines, take a look at the search tips page.

The advanced search option often provides more possibilities, for example searching for specific language documents, or for documents published after a certain date.

Special features, such as searching within a certain domain or website; searching for a specific file type; searching for web sites that link to a specific site; looking for synonyms; possibility to handle boolean searches; search for stop words; and the use of diacritics, are listed in the Special features table.

Limitations of a search engine

Search engines only index the first part of a web page: Yahoo! indexes the first 500 KB of a web page, Google not more than 101KB (10).

Search engines are databases of the past. Latest additions / new items might not be indexed yet.

A search engine will often not be able to search the so called ‘invisible web’ or ‘deep web’. This means that you will not find information:

• stored in database records (libraries, yellow pages);
• stored in pages that require login;
• stored in web pages not indexed by search engines, e.g. recent addition, or pages without links;
• hidden (deeply) in the site structure of a web site.