World Wide Web

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"The Web" and "WWW" redirect here. For other uses, see Web and WWW (disambiguation). For the world's first browser, see WorldWideWeb.
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Image:WWWlogo.png
WWW's historical logo designed by Robert Cailliau

The World Wide Web ("WWW" or simply the "Web") is a system of interlinked, hypertext documents that runs over the Internet. With a Web browser, a user views Web pages that may contain text, images, and other multimedia and navigates between them using hyperlinks.

The Web was first created around 1990 by the Englishman Tim Berners-Lee working at CERN in Geneva, Switzerland. As its inventor, Berners-Lee conceptualised the Web to be the Semantic Web where all its contents should be descriptively marked-up.

Contents

[edit] Basic terms

The World Wide Web is the combination of four basic ideas:

  • Hypertext: a format of information which allows, in a computer environment, one to move from one part of a document to another or from one document to another through internal connections among these documents (called "hyperlinks");
  • Resource Identifiers: unique identifiers used to locate a particular resource (computer file, document or other resource) on the network - this is commonly known as a URL or URI, although the two have subtle technical differences;
  • The Client-server model of computing: a system in which client software or a client computer makes requests of server software or a server computer that provides the client with resources or services, such as data or files; and
  • Markup language: characters or codes embedded in text which indicate structure, semantic meaning, or advice on presentation.

On the World Wide Web, a client program called a user agent retrieves information resources, such as Web pages and other computer files, from Web servers using their URLs. If the user agent is a kind of Web browser, it displays the resources on a user's computer. The user can then follow hyperlinks in each web page to other World Wide Web resources, whose location is embedded in the hyperlinks. It is also possible, for example by filling in and submitting web forms, to post information back to a Web server for it to save or process in some way. Web pages are often arranged in collections of related material called "Web sites." The act of following hyperlinks from one Web site to another is referred to as "browsing" or sometimes as "surfing" the Web.

The phrase "surfing the Internet" was first popularized in print by Jean Armour Polly, a librarian, in an article called Surfing the INTERNET, published in the University of Minnesota Wilson Library Bulletin in June, 1992. Although Polly may have developed the phrase independently, slightly earlier uses of similar terms have been found on the Usenet from 1991 and 1992, and some recollections claim it was also used verbally in the hacker community for a couple years before that.

For more information on the distinction between the World Wide Web and the Internet itself—as in everyday use the two are sometimes confused—see Dark internet where this is discussed in more detail.

Although the English word worldwide is normally written as one word (without a space or hyphen), the proper name World Wide Web and abbreviation WWW are now well-established even in formal English. The earliest references to the Web called it the WorldWideWeb (an example of computer programmers' fondness for CamelCase) or the World-Wide Web (with a hyphen, this version of the name is the closest to normal English usage).

Ironically, the abbreviation "WWW" is somewhat impractical as it contains two or three times as many syllables (depending on accent) as the full term "World Wide Web", and thus takes longer to say.

[edit] How the Web works

Viewing a Web page or other resource on the World Wide Web normally begins either by typing the URL of the page into a Web browser, or by following a hypertext link to that page or resource. The first step, behind the scenes, is for the server-name part of the URL to be resolved into an IP address by the global, distributed Internet database known as the Domain name system or DNS.

The next step is for an HTTP request to be sent to the Web server at that IP address, for the page required. In the case of a typical Web page, the HTML text is first requested and parsed by the browser, which then makes additional requests for graphics and any other files that form a part of the page in quick succession. This is the distinction between a single page view and the many hits or web requests that are often necessary to view the page.

The Web browser then renders the page as described by the HTML, CSS and other files received, incorporating the images and other resources as necessary. This produces the on-screen 'page' that the viewer sees.

Most Web pages will themselves contain hyperlinks to other relevant and informative pages and perhaps to downloads, source documents, definitions and other Web resources.

Such a collection of useful, related resources, interconnected via hypertext links, is what has been dubbed a 'web' of information. Making it available on the Internet created what Tim Berners-Lee first called the World Wide Web in the early 1990s [1] [2].

[edit] Caching

If the user returns to a page fairly soon, it is likely that the data will not be retrieved from the source Web server, as above, again. By default, browsers cache all web resources on the local hard drive. An HTTP request will be sent by the browser that asks for the data only if it has been updated since the last download. If it has not, the cached version will be reused in the rendering step.

This is particularly valuable in reducing the amount of web traffic on the internet. The decision about expiration is made independently for each resource (image, stylesheet, JavaScript file etc., as well as for the HTML itself). Thus even on sites with highly dynamic content, many of the basic resources are only supplied once per session or less. It is worth it for any Web site designer to collect all the CSS and JavaScript into a few site-wide files so that they can be downloaded into users' caches and reduce page download times and demands on the server.

There are other components of the Internet that can cache Web content. The most common in practice are often built into corporate and academic firewalls where they cache web resources requested by one user for the benefit of all. Some search engines such as Google also store cached content from Web sites.

Apart from the facilities built into Web servers that can ascertain when physical files have been updated, it is possible for designers of dynamically generated web pages to control the HTTP headers sent back to requesting users, so that pages are not cached when they should not be — for example Internet banking and news pages.

This helps with understanding the difference between the HTTP 'GET' and 'POST' verbs — data requested with a GET may be cached, if other conditions are met, whereas data obtained after POSTing information to the server usually will not.

[edit] Origins

See also: History of the Internet - CERN, Where the Web Was "WWW" born
Image:FirstWebServer.jpg
This NeXTcube used by Berners-Lee at CERN became the first Web server.

The underlying ideas of the Web can be traced as far back as 1980, when, at CERN in Switzerland, the Englishman Tim Berners-Lee built ENQUIRE (referring to Enquire Within Upon Everything, a book he recalled from his youth). While it was rather different from the Web we use today, it contained many of the same core ideas (and even some of the ideas of Berners-Lee's next project after the WWW, the Semantic Web).

In March 1989, Tim Berners-Lee wrote Information Management: A Proposal, which referenced ENQUIRE and described a more elaborate information management system. With help from Robert Cailliau, he published a more formal proposal for the World Wide Web on November 12, 1990.

A NeXTcube 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 [3]: the first Web browser (which was a Web editor as well), the first Web server and the first Web pages which described the project itself.

On August 6, 1991, he posted a short summary of the World Wide Web project on the alt.hypertext newsgroup. This date also marked the debut of the Web as a publicly available service on the Internet.

The crucial underlying concept of hypertext originated with older projects from the 1960s, such as 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".

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 tackled the project himself. In the process, he developed a system of globally unique identifiers for resources on the Web and elsewhere: the Uniform Resource Identifier.

The World Wide Web had a number of differences from other hypertext systems that were then available:

  • The WWW required only unidirectional links rather than bidirectional ones. This made 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 broken links.
  • 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 April 30, 1993, CERN announced<ref>http://intranet.cern.ch/Chronological/Announcements/CERNAnnouncements/2003/04-30TenYearsWWW/Welcome.html</ref> that the World Wide Web would be free to anyone, with no fees due. Coming two months after the announcement that gopher 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 which was based upon HyperCard. The World Wide Web, however, only gained critical mass with the 1993 release of the graphical Mosaic web browser by the National Center for Supercomputing Applications developed by Marc Andreessen. Prior to the release of Mosaic, graphics were not commonly mixed with text in Web pages and its popularity was less than older protocols in use over the Internet, such as Gopher protocol and Wide area information server. Mosaic's graphical user interface allowed the Web to become by far the most popular Internet protocol.

[edit] Web standards

At its core, the Web is made up of three standards:

  • the Uniform Resource Identifier (URI), which is a universal system for referencing resources on the Web, such as Web pages;
  • the HyperText Transfer Protocol (HTTP), which specifies how the browser and server communicate with each other; and
  • the HyperText Markup Language (HTML), used to define the structure and content of hypertext documents.

Berners-Lee now heads the World Wide Web Consortium (W3C), which develops and maintains these and other standards that enable computers on the Web to effectively store and communicate different forms of information.

[edit] Java and JavaScript

Another significant advance in the technology was Sun Microsystems' Java platform. It initially enabled Web servers to embed small programs (called applets) directly into the information being served, and these applets would run on the end-user's computer, allowing faster and richer user interaction. Eventually, it came to be more widely used as a tool for generating complex server-side content as it is requested. Java never gained as much acceptance as Sun had hoped as a platform for client-side applets for a variety of reasons, including lack of integration with other content (applets were confined to small boxes within the rendered page) and poor performance (particularly start up delays) of Java VMs on PC hardware of that time.

JavaScript, however, is a scripting language that was developed for Web pages. The standardised version is ECMAScript. While its name is similar to Java, it was developed by Netscape and not Sun Microsystems, and it has almost nothing to do with Java, with the only exception being that like Java its syntax is derived from the C programming language. Like Java, JavaScript is also object oriented, but like C++ and unlike Java, it allows mixed code—both object-oriented as well as procedural. In conjunction with the Document Object Model, JavaScript has become a much more powerful language than its creators originally envisioned. Sometimes its usage alongside CSS and manipulation of the Document Object Model is expressed under the term Dynamic HTML (DHTML), to emphasise a shift away from static HTML pages.

Ajax (Asynchronous JavaScript And XML) is a JavaScript-based technology that may have a significant effect on the development of the World Wide Web. By providing a method where only part of a page need be updated when required, rather than the whole, Ajax allows such updates to be much faster and more efficient. Ajax is seen as an important aspect of Web 2.0. Examples of Ajax techniques currently in use can be seen in Gmail, Google Maps etc.

[edit] Sociological implications

The Web, as it stands today, has allowed global interpersonal exchange on a scale unprecedented in human history. People separated by vast distances, or even large amounts of time, can use the Web to exchange—or even mutually develop—their most intimate and extensive thoughts, or alternately their most casual attitudes and spirits. Emotional experiences, political ideas, cultural customs, musical idioms, business advice, artwork, photographs, literature, can all be shared and disseminated digitally with less individual investment than ever before in human history. Although the existence and use of the Web relies upon material technology, which comes with its own disadvantages, its information does not use physical resources in the way that libraries or the printing press have. Therefore, propagation of information via the Web (via the Internet, in turn) is not constrained by movement of physical volumes, or by manual or material copying of information. By virtue of being digital, the information of the Web can be searched more easily and efficiently than any library or physical volume, and vastly more quickly than a person could retrieve information about the world by way of physical travel or by way of mail, telephone, telegraph, or any other communicative medium.

The Web is the most far-reaching and extensive medium of personal exchange to appear on Earth. It has probably allowed many of its users to interact with many more groups of people, dispersed around the planet in time and space, than is possible when limited by physical contact or even when limited by every other existing medium of communication combined.

Because the Web is global in scale, some have suggested that it will nurture mutual understanding on a global scale. By definition or by necessity, the Web has such a massive potential for social exchange, it has the potential to nurture empathy and symbiosis, but it also has the potential to incite belligerence on a global scale, or even to empower demagogues and repressive regimes in ways that were historically impossible to achieve previously.

[edit] Publishing Web pages

The Web is available to individuals outside mass media. In order to "publish" a Web page, one does not have to go through a publisher or other media institution, and potential readers could be found in all corners of the globe.

Unlike books and documents, hypertext does not have a linear order from beginning to end. It is not broken down into the hierarchy of chapters, sections, subsections, etc.

Many different kinds of information are now available on the Web, and for those who wish to know other societies, their cultures and peoples, it has become easier. When travelling in a foreign country or a remote town, one might be able to find some information about the place on the Web, especially if the place is in one of the developed countries. Local newspapers, government publications, and other materials are easier to access, and therefore the variety of information obtainable with the same effort may be said to have increased, for the users of the Internet.

Although some Web sites are available in multiple languages, many are in the local language only. Additionally, not all software supports all special characters, and RTL languages. These factors would challenge the notion that the World Wide Web will bring a unity to the world.

The increased opportunity to publish materials is certainly observable in the countless personal pages, as well as pages by families, small shops, etc., facilitated by the emergence of free Web hosting services.

[edit] Statistics

According to a 2001 study<ref>http://www.brightplanet.com/technology/deepweb.asp</ref>, there were more than 550 billion documents on the Web, mostly in the "invisible Web". A 2002 survey of 2,024 million Web pages<ref>http://www.netz-tipp.de/languages.html</ref> determined that by far the most Web content was in English: 56.4%; next were pages in German (7.7%), French (5.6%) and Japanese (4.9%). A more recent study which used web searches in 75 different languages to sample the Web determined that there were over 11.5 billion web pages in the publicly indexable Web as of January 2005.<ref>http://www.cs.uiowa.edu/~asignori/web-size/</ref>

[edit] Speed issues

Frustration over congestion issues in the Internet infrastructure and the high latency that results in slow browsing has led to an alternative name for the World Wide Web: the World Wide Wait. Speeding up the Internet is an ongoing discussion over the use of peering and QoS technologies. Other solutions to reduce the World Wide Wait can be found on W3C.

Standard guidelines for ideal Web response times are (Nielsen 1999, page 42):

  • 0.1 second (one tenth of a second). Ideal response time. The user doesn't sense any interruption.
  • 1 second. Highest acceptable response time. Download times above 1 second interrupt the user experience.
  • 10 seconds. Unacceptable response time. The user experience is interrupted and the user is likely to leave the site or system.

These numbers are useful for planning server capacity.

[edit] Link rot

The Web suffers from link rot, links becoming broken because of the continual disappearance or relocation of Web resources over time. The ephemeral nature of the Web has prompted many efforts to archive the Web. The Internet Archive is one of the most well-known efforts; they have been archiving the Web since 1996.

Ultimately, dead links are the price we pay for the World Wide Web; the web's scale and infrastructure make it impossible to monitor all hyperlinks in real time, and there is no broadcast notification when a page is removed ( like a star going supernova ) or renamed. Allowing links between resources carries the inherent danger that some of the links will be invalidated over time.

[edit] Academic conferences

The major academic event covering the WWW is the World Wide Web series of conferences, promoted by IW3C2. There is a list with links to all conferences in the series.

[edit] WWW prefix in Web addresses

"WWW" is commonly found at the beginning of Web addresses. Many organizations on the Internet follow the convention of naming hosts according to the services they provide. So for example, the host name for a Web server is "www"; for an FTP server it's "ftp"; or a news server is "news" or "nntp" (after the news protocol NNTP). The host names are then used as DNS subdomain names, giving the full "www.example.com".

These prefixes are not required by any technical standard; indeed, the first Web server was at "info.cern.ch" [citation needed] and even today many Web sites are available without the "www" prefix. The "www" prefix has no meaning in the way the main website is shown; locally or around the world. The "www" prefix is simply a subdomain.

Some Web browsers will automatically try adding "www." to the beginning, and possibly ".com" to the end, of host names in typed URLs if a host is not found without them. Internet Explorer and Mozilla Firefox will automatically prefix 'http://www.' and append '.com' to the address bar contents when the Control and Enter keys are pressed simultaneously. For example, entering "example" in the address bar and then pressing Control+Enter causes the browser to visit "http://www.example.com".

[edit] Pronunciation of "www"

In English, WWW is the longest possible three-letter acronym (TLA) to pronounce, requiring nine syllables. The late Douglas Adams once quipped:

The World Wide Web is the only thing I know of whose shortened form takes three times longer to say than what it's short for.

—Douglas Adams, The Independent on Sunday, 1999

Shorter variants include "triple 'double u'", "triple dub", "dub dub dub", "wuh wuh wuh," and "all the 'double u's". In other languages, "www" is often pronounced as "vvv" or "3w". The early "w³" abbreviation is nowadays deprecated.

In Chinese, the World Wide Web is commonly translated to wàn wéi wǎng (万维网), i.e. "ten-thousand dimensional net".

[edit] Trivia

  • The first Web site went on-line in 1991. On April 30 1993, CERN announced that the World Wide Web would be free to anyone. A copy of the original first Web page, created by Tim Berners-Lee, is kept here.<ref>[4] Wikipedia.com Retrieved on 2006-8-10</ref>

[edit] Standards

Main article: W3C

The following is a cursory list of the documents that define the World Wide Web's three core standards:

[edit] See also

[edit] References

[edit] External links

Image:Steps.svg
Preceding: ENQUIRE
Subsequent:


[edit] Wikibooks

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