| Every day we use Internet services and search engines in particular when looking for data. The search results are normally provided in the form of a list and are normally called hits. The data may comprise web pages, images, data and other types of files. Some search engines also collect information available in databanks or open directories. Unlike Internet directories that are maintained by human editors, search tools operate algorithmically or are a mix of human and algorithmic input.
Web search engines function by storing information about a huge number of web pages which they retrieve from the INTERNET. These pages are retrieved by a web crawler, also known as a spider. It is an automatically-controlled Web browser that follows every link it discovers. The content of each page is then analyzed to decide how to index it. Words, for example, are extracted from titles, headings and subheadings or special fields called meta tags. Data about web pages are saved and stored in an index database for further use in queries. Some search engines, such as Google, store the entire or part of the source page (also called a cache) as well as information about web pages, while others, such as AltaVista, save and store every word of every page they find. This cached page always comprises the initial search text, since it is the one that was actually indexed. Thus, it can be very helpful as it contains data that may no longer be available elsewhere.
As soon as a web user has typed search terms in the search field, the tool browse through its index and provides a listing of the most suitable web pages according to its parameters, normally with a short summary containing the document's title and at times excerpts from the text. Some search engines have installed an advanced tool called proximity search which allows users to determine the length between search terms.
The relevancy of the results determines the usefulness of a search engine. Since there can be millions of web pages that comprise a particular key term or phrase, some pages may be more relevant and popular than others. Most search engines apply techniques to rank the results to list the "best" results first.
The way a search engine displays web pages varies from one engine to another. The methods also change over time, as the use of Internet services undergoes alterations and advanced techniques are employed. |
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