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Have a Better Look At Search Engines |
| Date Added: October 24, 2009 03:51:58 PM |
| Author: Martin |
| Category: Education And Reference |
| Every day we use the Web and search tools in particular when searching for information. The search results are commonly called hits and are provided in the form of a list. The data may comprise web pages, images, data and other types of files. Some search tools also gather data available in databanks or open directories. In comparison with Web directories which are maintained by human editors, search tools work automatically or are a mixture of human and algorithmic input. Internet search tools function by storing information about countless web pages which they retrieve from the WWW. These pages are retrieved by a web crawler, also known as a spider. It is an automated Web browser which follows every link it discovers. After that the content of each page is analyzed to determine how it should be indexed. Words, for instance, are extracted from titles, headings and subheadings or special fields called meta tags. Data about web pages are stored in an index databank for further use in queries. Some search engines, such as Google, save and store the entire or part of the source page (referred to as a cache) as well as data about web pages, whereas others, such as AltaVista, save and store every word of every page they find. The cached page always contains the actual search text, as it is the one that was actually indexed. Consequently, it can be very useful because it comprises data that can no longer be found anywhere else on the Internet. As soon as a web user has typed search words in the search field, the engine looks through its index and shows a listing of the most suitable web pages according to its criteria, usually with a brief summary combined with the title of the document and sometimes parts of the text. Some search tools have introduced an advanced option called proximity search that allows users to determine the length between search terms. The relevancy of the results determines the usefulness of a search engine. Since there may be millions of web pages containing a particular word or phrase, some pages may be more relevant and popular than others. Most search tools employ methods to grade the results to list the "best" results first. How a search engine determines which pages are the best matches, and in what arrangement the results should be displayed, varies from one engine to another. The techniques also change in time, as the use of the Internet alters and new techniques are developed. |
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