A Web Search Engine: How It Functions

A web search engine is a software program specially-designed to search for information on the World Wide Web. The search results are usually presented in the form of a list and are normally called hits. The data may consist of web pages, images, information and other types of files. Some search tools also accumulate information available in databanks or open directories. In comparison with Internet directories that are maintained by human editors, search tools function algorithmically or are a mix of human and algorithmic input. Web search tools operate by storing information about countless web pages which they retrieve from the WWW. These pages are retrieved by An Internet crawler, or differently called a spider. It is an automatically-controlled Web browser that follows every link it finds. After that the content of each page is analyzed to decide how to index it. Words, for example, are removed from titles, headings and subheadings or special fields called meta tags. Data about web pages are saved and stored in an index catalogue for further use in queries. Some search tools, such as Google, save and store the whole or part of the source page (referred to as a cache) as well as data about web pages, while others, such as AltaVista, save and store every word of every page they have found. This cached page always contains the initial search text, since it is the one that was actually indexed. Therefore, it can be very useful as it holds data that may no longer be available elsewhere. When a web user types key words in the search field, the engine browse through its database and displays a listing of best-matching web pages according to its parameters, commonly with a brief summary containing the document's title and at times extracts from the text. Some search engines offer an advanced feature called proximity search which allows users to determine the distance between search terms. The usefulness of a search engine rests on the relevance of the result set it provides. Since there may be millions of web pages containing a certain word or word combination, some pages may appear to be more relevant and popular than others. The vast majority of search tools use techniques to grade the results to list the "best" results first. The way a search software programme ranks web pages is search engine-specific. The methods also alter over time, as the use of Internet services alters and new techniques are developed.