World Wide Web

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From Wikipedia, the free encyclopedia

The World Wide Web (www, W3) is an information system of interlinked hypertext documents that are accessed via the Internet.^[1] It has also commonly become known simply as the Web. Individual document pages on the World Wide Web are called web pages and are accessed with a software application running on the user's computer, commonly called a web browser. Web pages may contain text, images, videos, and other multimedia components, as well as web navigation features consisting of hyperlinks.

Tim Berners-Lee, a British computer scientist and former CERN employee,^[2] is considered the inventor of the Web. On 12 March 1989,^[3] Berners-Lee wrote a proposal for what would eventually become the World Wide Web.^[4] The 1989 proposal was meant for a more effective CERN communication system but Berners-Lee eventually realised the concept could be implemented throughout the world.^[5] Berners-Lee and Belgian computer scientist Robert Cailliau proposed in 1990 to use hypertext "to link and access information of various kinds as a web of nodes in which the user can browse at will",^[6] and Berners-Lee finished the first website in December of that year.^[7] The first test was completed around 20 December 1990 and Berners-Lee reported about the project on the newsgroup alt.hypertext on 7 August 1991.^[8]

§History

The NeXT Computer used by Tim Berners-Lee at CERN.

On March 12, 1989, Tim Berners-Lee wrote a proposal to the management at CERN that referenced ENQUIRE, a database and software project he had built in 1980, and described a more elaborate information management system based on links embedded in readable text: "Imagine, then, the references in this document all being associated with the network address of the thing to which they referred, so that while reading this document you could skip to them with a click of the mouse." Such a system, he explained, could be referred to using one of the existing meanings of the word hypertext, a term that he says was coined in the 1950s. There is no reason, the proposal continues, why such hypertext links could not encompass multimedia documents including graphics, speech and video, so that Berners-Lee goes on to propose the term hypermedia.^[9]

With help from Robert Cailliau, he published a more formal proposal (on 12 November 1990) to build a "Hypertext project" called "WorldWideWeb" (one word, also "W3") as a "web" of "hypertext documents" to be viewed by "browsers" using a client–server architecture.^[6] This proposal estimated that a read-only web would be developed within three months and that it would take six months to achieve "the creation of new links and new material by readers, [so that] authorship becomes universal" as well as "the automatic notification of a reader when new material of interest to him/her has become available." While the read-only goal was met, accessible authorship of web content took longer to mature, with the wiki concept, WebDAV, blogs, Web 2.0 and RSS/Atom.^[10]

The proposal was modeled after the SGML reader Dynatext by Electronic Book Technology, a spin-off from the Institute for Research in Information and Scholarship at Brown University. The Dynatext system, licensed by CERN, was a key player in the extension of SGML ISO 8879:1986 to Hypermedia within HyTime, but it was considered too expensive and had an inappropriate licensing policy for use in the general high energy physics community, namely a fee for each document and each document alteration.

The CERN data center in 2010 housing some WWW servers

A NeXT Computer was used by Berners-Lee as the world's first web server and also to write the first web browser, WorldWideWeb, in 1990. By Christmas 1990, Berners-Lee had built all the tools necessary for a working Web:^[11] the first web browser (which was a web editor as well); the first web server; and the first web pages,^[12] which described the project itself.

The first web page may be lost, but Paul Jones of UNC-Chapel Hill in North Carolina announced in May 2013 that Berners-Lee gave him what he says is the oldest known web page during a 1991 visit to UNC. Jones stored it on a magneto-optical drive and on his NeXT computer.^[13]

On 6 August 1991, Berners-Lee published a short summary of the World Wide Web project on the newsgroup alt.hypertext.^[14] This date also marked the debut of the Web as a publicly available service on the Internet, although new users only access it after August 23. For this reason this is considered the internaut's day. Several newsmedia have reported that the first photo on the Web was published by Berners-Lee in 1992, an image of the CERN house band Les Horribles Cernettes taken by Silvano de Gennaro; Gennaro has disclaimed this story, writing that media were "totally distorting our words for the sake of cheap sensationalism."^[15]

The first server outside Europe was installed at the Stanford Linear Accelerator Center (SLAC) in Palo Alto, California, to host the SPIRES-HEP database. Accounts differ substantially as to the date of this event. The World Wide Web Consortium says December 1992,^[16] whereas SLAC itself claims 1991.^[17][18] This is supported by a W3C document titled A Little History of the World Wide Web.^[19]

The underlying concept of hypertext originated in previous projects from the 1960s, such as the Hypertext Editing System (HES) at Brown University, Ted Nelson's Project Xanadu, and Douglas Engelbart's oN-Line System (NLS). Both Nelson and Engelbart were in turn inspired by Vannevar Bush's microfilm-based memex, which was described in the 1945 essay "As We May Think".^[20]

Berners-Lee's breakthrough was to marry hypertext to the Internet. In his book Weaving The Web, he explains that he had repeatedly suggested that a marriage between the two technologies was possible to members of both technical communities, but when no one took up his invitation, he finally assumed the project himself. In the process, he developed three essential technologies:

• a system of globally unique identifiers for resources on the Web and elsewhere, the universal document identifier (UDI), later known as uniform resource locator (URL) and uniform resource identifier (URI);
• the publishing language HyperText Markup Language (HTML);
• the Hypertext Transfer Protocol (HTTP).^[21]

The World Wide Web had a number of differences from other hypertext systems available at the time. The Web required only unidirectional links rather than bidirectional ones, making it possible for someone to link to another resource without action by the owner of that resource. It also significantly reduced the difficulty of implementing web servers and browsers (in comparison to earlier systems), but in turn presented the chronic problem of link rot.
Unlike predecessors such as HyperCard, the World Wide Web was non-proprietary, making it possible to develop servers and clients independently and to add extensions without licensing restrictions. On 30 April 1993, CERN announced that the World Wide Web would be free to anyone, with no fees due.^[22] Coming two months after the announcement that the server implementation of the Gopher protocol was no longer free to use, this produced a rapid shift away from Gopher and towards the Web. An early popular web browser was ViolaWWW for Unix and the X Windowing System.

Robert Cailliau, Jean-François Abramatic of IBM, and Tim Berners-Lee at the 10th anniversary of the World Wide Web Consortium.

Scholars generally agree that a turning point for the World Wide Web began with the introduction^[23] of the Mosaic web browser^[24] in 1993, a graphical browser developed by a team at the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign (NCSA-UIUC), led by Marc Andreessen. Funding for Mosaic came from the U.S. High-Performance Computing and Communications Initiative and the High Performance Computing and Communication Act of 1991, one of several computing developments initiated by U.S. Senator Al Gore.^[25] Prior to the release of Mosaic, graphics were not commonly mixed with text in web pages and the web's popularity was less than older protocols in use over the Internet, such as Gopher and Wide Area Information Servers (WAIS). Mosaic's graphical user interface allowed the Web to become, by far, the most popular Internet protocol.

The World Wide Web Consortium (W3C) was founded by Tim Berners-Lee after he left the European Organization for Nuclear Research (CERN) in October 1994. It was founded at the Massachusetts Institute of Technology Laboratory for Computer Science (MIT/LCS) with support from the Defense Advanced Research Projects Agency (DARPA), which had pioneered the Internet; a year later, a second site was founded at INRIA (a French national computer research lab) with support from the European Commission DG InfSo; and in 1996, a third continental site was created in Japan at Keio University. By the end of 1994, the total number of websites was still relatively small, but many notable websites were already active that foreshadowed or inspired today's most popular services.

Connected by the existing Internet, other websites were created around the world, adding international standards for domain names and HTML. Since then, Berners-Lee has played an active role in guiding the development of web standards (such as the markup languages to compose web pages in), and has advocated his vision of a Semantic Web. The World Wide Web enabled the spread of information over the Internet through an easy-to-use and flexible format. It thus played an important role in popularizing use of the Internet.^[26] Although the two terms are sometimes conflated in popular use, World Wide Web is not synonymous with Internet.^[27] The Web is an information space containing hyperlinked documents and other resources, identified by their URIs.^[28] It is implemented as both client and server software using Internet protocols such as TCP/IP and HTTP.

Tim Berners-Lee was knighted in 2004 by Queen Elizabeth II for his contribution of the World Wide Web.^[29]

§Function[edit]

The World Wide Web functions as a layer on top of the Internet, helping to make it more functional. The advent of the Mosaic web browser helped to make the web much more usable.

The terms Internet and World Wide Web are often used without much distinction. However, the two things are not the same. The Internet is a global system of interconnected computer networks. In contrast, the World Wide Web is one of the services transferred over these networks. It is a collection of text documents and other resources, linked by hyperlinks and URLs, usually accessed by web browsers, from web servers.^[30]

Viewing a web page on the World Wide Web normally begins either by typing the URL 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, window surfing, evolved surfing, bounded navigation and targeted navigation.^[31]

The following example demonstrates the functioning of web browser when accessing a page at the URL http://example.org/wiki/World_Wide_Web. The browser resolves the server name of the URL (example.org) into an Internet Protocol address using the globally distributed Domain Name System (DNS). This lookup returns an IP address such as 203.0.113.4. The browser then requests the resource by sending an HTTP request 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 the 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:

GET /wiki/World_Wide_Web HTTP/1.1
Host: example.org

The computer receiving the HTTP request delivers it to web server software listening for requests on port 80. If the web server can fulfill the request it sends an HTTP response back to the browser indicating success:

HTTP/1.0 200 OK
Content-Type: text/html; charset=UTF-8

followed by the content of the requested page. The Hypertext Markup Language for a basic web page looks like The World Wide Web, abbreviated as WWW and commonly known ...


The web browser parses the HTML and interprets the markup (