What is World Wide Web(www) and Search Engine?

                                WORLD WIDE WEB

The World Wide Web (abbreviated WWW or the Web) is an information space where documents and other web resources are identified by Uniform Resource Locators (URLs), interlinked by hypertext links, and can be accessed via the internet. English scientist Tim Berners-Lee invented the World Wide Web in 1989 while employed at CERN in Switzerland. The Web browser was released outside of CERN in 1991, first to other research institutions starting in January 1991 and to the general public on the internet in August 1991.

The World Wide Web has been central to the development of the information Age and is the primary tool billions of people use to interact on the internet. Web pages are primarily text documents formatted and annotated with Hyper Text Markup Language (HTML). In addition to formatted text, web pages may contain images, video, audio, and software components that are rendered in the user’s web browser as coherent pages of multimedia content.

Embedded Hyperlinks  permits users to navigate between web pages.  Multiple web pages with a common theme, a common domain name, or both, make up a website. Website content can largely be provided by the publisher or interactive where users contribute content or the content depends upon the user or their actions. Website may be mostly informative, primarily for entertainment, or largely for commercial, governmental, or non-governmental organization purpose. In the 2006 Great British Design Quest organized by the BBC and the design Museum, the World Wide Web was voted among the 10 British design icons.

The terms Internet and World Wide Web are often used without much distinction. However, the two are not the same. The Internet is a global system of interconnected computer networks. In contrast, the World Wide Web is a Global collection of documents and other resources, linked by hyperlinks and URLs.

Web resources are usually accessed using HTTP, which is one of many Internet communication protocols.

Viewing a web page on the World Wide Web normally begins either by typing the URLs of the page into a web browser, or by following a hyperlink to that page or resource. The web browser then initiates a series of background communication messages to fetch and display the requested page. In the 1990s, using a browser to view web pages- and to move from one web page to another through hyperlinks- came to be known as “browsing’, ‘web surfing’ (after channel surfing), or ‘navigating the web’. Early studies of this new behavior investigated user patterns in using web browsers. One study, for example, found five user patterns: exploratory surfing, windows surfing, evolved surfing, bounded navigation and targeted navigation.

The following example demonstrates the functioning of a web browser when accessing a page at the

URLhttp://www.example.org/home.html. The browser resolves the server name of the URL (www.example.org) into an Internet Protocol address using the globally distributed Domain Name System (DNS). This lookup returns an IP address such as 304.0.224.5 or 3002:db9:3e::8445. The browser then requests the resources by sending an HTTP requests across the Internet to the computer at that address. It requests service from a specific TCP port number that is well known for the HTTP service, so that receiving host can distinguish an HTTP request from other network protocols it may be servicing. The HTTP protocol normally uses port number 80. The content of the HTTP request can be as simple as two lines of text:

JavaScript is a scripting language that was initially developed in 1995 by Brendan  Eich, then of Netscape , for use within web pages.[35] The standardised   version is ECMA scripts.[35] To make web pages more interactive, some web applications also use JavaScript techniques such as Ajax (asynchronous Java Script and XML). Client – side script is delivered with the page that can make additional HTTP request to the server, either in response to user actions such as mouse movements or clicks, or based on elapsed time. The server’s response are used to modify the current page rather than creating a new page with each response, the server needs only to provide limited, incremental information. Multiple Ajax request can be handled at the same time, and users can interact with the page while data is retrieved. Web pages may also regularly poll the server to check whether new information is available many hostnames used for the World Wide Web begin with www because of the long-standing practice of naming Internet hosts according to the services they provide.

 The hostname of a web server is often www, in the same way that it be ftp for an FTP server, and news or nntp for a USENET news server. Theses host names appear as Domain Name System (DNS) or sub-domain names, as in www.example.com. The use of www is not required by ant technical or policy standard and many web sites do not use it; indeed, the first ever web server was called nxoc01.cern.ch.  According to Paolo Palazzi, who worked at CERN along with Tim Berners -lee, the popular use of www as sub-domain was accidental; the World Wide Web project page was intended to be published at www.cern.ch while info.cern.ch was intended to be the CERN home page, however the DNS records were never switched, and the practice of prepending www to an institution’s website domain name was subsequently copied.

 Many established websites still use the prefix, or they employ other sub-domain names such as www2, secure or en for special purposes. Many such web servers are set up so that both the main domain name (e.g., www.example.com) refer to the same site; others require one form or the other, or they may map to different web sites. The use of a sub-domain name is useful for load balancing incoming web traffic by creating a CNAME record that points to a cluster of web servers. Since, currently, only a sub-domain can be used in a CNAME, the same result cannot be achieved by using the bare domain root.[citation needed]

For example, entering ‘Microsoft’ may be transformed to http://www.microsoft.com/ and ‘open office’ to http://www.openoffice.org.

                                   SEARCH ENGINE

A Web search engine is a software system that is designed to search for information on the World Wide Web. The search results are generally presented in a line of results often referred to as search engine results pages (SERPs). The information may be a mix of web pages, images, and other types of lines. Some search engine also mine data available in databases or open directories.

 Unlike web directories, which are maintained only by human editors, search engine also maintain real-time information by running an algorithm on a web crawler. Web search engines get their information by web crawling from site to site. The “spider” checks for the standard filename robots.txt, addressed to it, before sending certain information back to be indexed depending on many factors, such as the titles, page content, JavaScript, Cascading Style Sheets (CSS), heading as evidenced by the standard HTML markup of the informational content, or its metadata in HTML meta tags.

Indexing means associating words and other definable tokens found on web pages to their domain names and HTML - based fields. The associations are made in a public database, made available for web search queries. A query from a user can be a single word. The index helps find information relating to the query as quickly as possible.

Some of the techniques for index, and caching are trade secrets, whereas web crawling is a straight forward process of visiting all sites on a systematic basis.

Between visits by the spider, the cached version of page (some or all the content need to render it) stored in the search engine working memory is quickly sent to an inquirer. If a visit is overdue, the search engine can just act as a web proxy instead. In this case the page may differ from the search terms indexes. The cached page holds the appearance of the version whose words were indexed, so a cached version of a page can be useful to the web site when the actual page has been lost, but this problem is also considered a mind form of link rot.

Beyond simple keyword lookups, search engines offer their own GUI- or command – driven operators and search parameters to refine the search results. These provide the necessary controls for the user engaged in the feedback loop users create by filtering and weighting while reefing the search results, given the initial pages of the first search results. For example, from 2007 the ZGoohle.com search engine has allowed one to filter by date by clicking “Show search tools” in the leftmost column of the initial search results page, and then selecting the desired date range.

 It’s also possible to weight by date because each page has a modification time. Most search engines supports the use of the Boolean operators AND, OR and NOT to help end users refine the search query. Boolean operators are for literal searches that allow the user to refine and extended the terms of the search. The engine looks for the words or phrases exactly as entered. Some search engine provide an advanced feature called proximity search, which allows users to define the distance between keywords.

 There is also concept-based searching where the research  involve using statistical analysis on pages containing the words or phrases you search for. As well, natural language queries allow user to type a question in the same form one would ask it to a human. Asite like this would be ask.com. The usefulness of a search engine depends on the relevance of the result set it gives back. While there may be millions of web pages that include a particular word or phrase, some pages may be more relevant, popular, or authoritative than others.

Most search engines employ methods to rank the results to provide the “best” results first. How a search engine decides which pages are the best matches, and what order the results should be shown in, varies widely from one engine to another. The methods also change over time as internet usage changes and new techniques evolved. There are two main types of search engine that have evolved: one is a system of predefined and hierarchically ordered keywords that humans have programmed extensively.