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Search Engines - An In Depth Analysis |
| Every day we use the Internet and search engines in particular when looking for information. The search results are commonly called hits and are presented in the form of a list. The information may contain web pages, images, information and other types of files. Some search tools also collect information available in databases or open directories. Unlike Internet directories which are maintained by human editors, search engines operate automatically or are a mix of human and algorithmic input.Web search tools work by storing information about a huge number of web pages which they retrieve from the WWW. These pages are retrieved by a web crawler, or differently called a spider. It is an automatically-controlled Web browser which follows every link it sees. The content of each page is then analyzed to decide how it should be indexed. Words, for instance, are extracted from titles, headings or special fields called meta tags. Data about web pages are stored in an index database for further use in queries. Some search tools, such as Google, save and store the entire or part of the source page (known as a cache) as well as information about web pages, whereas others, such as AltaVista, save and store every word of every page they have found. This cached page always holds the actual search text, since it is the one that was actually indexed. So, it can be very useful when the content of the current page has been updated and the search words are no longer in it.When an Internet user types search words in the search field, the software program looks through its databank and provides a listing of best-matching web pages in accordance with its parameters, normally with a short summary containing the title of the document and at times extracts from the text. Some search engines have installed an advanced option called proximity search that allows users to determine the distance between search terms.The usefulness of a search engine rests on the relevancy of the result set it provides. Since there may be millions of web pages containing a certain search term or word combination, some pages may be more relevant and popular than others. The results can be ranked to show the "best" ones first.The way a search software program displays web pages varies from one engine to another. The techniques also change in time, because the use of Internet services alters as more advanced techniques become available. |