World Wide Web

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Revision as of 15:38, 4 April 2007 by imported>Pat Palmer (first revision of opening paragraph)
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"The Web" and "WWW" redirect here.
WWW's historical logo designed by Robert Cailliau

The World Wide Web ("www" or simply the "web") is a global collection of information presented in the form of documents hosted on networked computers and available to the public. The information includes text files, images, videos, sound files and many other types of information. The documents containing information are delivered to individuals over a global computer network called the Internet.

The Internet is but the transport mechanism. After connecting to the Internet, people can browse the web by running a web browser on their local computer and using the web browser to surf (move around at will) through the vast array of available web documents. Connecting to the Internet also enables people to use many other services which are not necessarily considered to be part of the world wide web, such as e-mail, instant messaging or [Voice over IP]][1].

Web technical specifications

The world wide web is implemented by software which adheres at least to the following three standards:

  • the Uniform Resource Identifier (URI)[2], which is a universal system for referencing resources on the Web, such as Web pages;
  • the HyperText Transfer Protocol (HTTP)[3], which specifies how the browser and server communicate with each other
  • the HyperText Markup Language (HTML)[4], used to define the structure and content of hypertext documents.

How the Web works

Web pages, and other files (such as images and videos), on the World Wide Web are stored on many different web servers located all around the world. These web servers are all connected to the the Internet. The user accesses the Web through the Internet using a user agent program, such as a web browser (a type of user agent that renders and displays the requested web page to the user). The user can navigate to different pages on the web by either typing in the Uniform Resource Identifier (URI)[5], also referred to as the "web address" (for example http://pilot.citizendium.org/wiki/World_Wide_Web) into the web browser, or by following a hyperlink from another web page. The user agent uses this URI to figure out which web server to ask for which resource and using which communication protocol. Unless a problem has occured, the server sends back the requested resource.

Hypertext

For more information, see: Hypertext.


Web Addresses

For more information, see: Uniform Resource Identifier.

On the Internet, a site is commonly identified to users by a domain name (such as www.google.com), while computers usually use Internet Protocol (IP) addresses (such as 209.85.135.104). To avoid forcing users to remember complex strings of numbers, browsers use Domain Name Service (DNS) routers, which act as phonebooks, matching the domain name with an IP address.

A web address consists of several parts. An example URI might be:[6] 

http://www.w3.org:80/Consortium/activities.html#HTMLActivity
  • http:// tells the browser to use the HTTP protocol.
  • www.w3.org refers to the specific server. The browser would look this up with DNS.
  • :80 refers to the port (networking) port. The default HTTP port is 80, and generally isn't included in an address.
  • /Consortium/ is the path on the server. Like on desktops, most websites are organized in a folder-based heirarchy.
  • activities.html refers to the specific web page.
  • #HTMLActivity is called a "fragment". It directs the browser to a section on the actual page.

Web addresses frequently start with "www". The first part of the web address indicates the specific service you wish to access. In the case of news.google.com, this means "Google.com's website, specifically the servers that handle 'news'." The reason that "www" is so common is that customarily, different services or protocols are handled under different hostnames. For instance, public FTP was traditionally done from "ftp.name.org", while Gopher would have been handled by "gopher.name.org". This convention predated the World Wide Web, and so organizations began calling web servers "www" servers. Some sites still require the "www", while other sites don't.

Web servers

For more information, see: web server.

A web server is a computer which serves HTML pages to web browsers on request. A web server often uses more expensive hardware than personal computers, but any computer can function as a web server. Web servers run specialized web server software, such as Apache or Microsoft's IIS. Web servers can serve static webpages or dynamic webpages to requesting web browsers.

Communication

See also: HTTP and Internet protocol suite

To allow efficient communication between client and web servers a Hyper Text Transfer Protocol (or HTTP) is used. To request a web page the client’s web browser sends a request message to the server formatted in a way described by the HTTP protocol. If a problem has occurred then the server sends back a reply describing the problem, otherwise it sends back the web page. Similarly if the client needs to upload something to a web server, the data is sent formatted in HTTP.

These HTTP messages are sent over the Internet using the TCP/IP protocol suite. Web Browsers frequently cache web sites, allowing them to keep a local copy of the site. When the site is reaccessed, the web browser only re-requests the parts of the site that have changed.

Origins

For more information, see: History of the World Wide Web.
See also: History of the Internet
File: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, Tim Berners-Lee built ENQUIRE - a system which contained many of the same core ideas for the modern Web.[7] In 1990 Berners-Lee created the first web server and also wrote the first web browser, called WorldWideWeb. The Web made its debut as a publically available service on August 6, 1991.[8][7]

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).[9]

On April 30, 1993, CERN announced that the World Wide Web would be free to anyone.[10] This came two months after the announcement that gopher, the older distributed document protocol, was no longer free to use.[11]

The World Wide Web, however, only gained critical mass after the 1993 release of the graphical Mosaic web browser by the National Center for Supercomputing Applications (NCSA) 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.


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.

Content

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. 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. It's free to post some smaller webpages, and even larger sites are inexpensive in comparison to traditional media.

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. This allows readers to easily find more on a topic, move to other related topics, or skip sections they're uninterested in.

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 websites are available in multiple languages, many are in the local language only. Also, 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.

Link rot

Link rot is when web links become broken due to resources moving or ceasing to exist. 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.

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. And 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.

Web 2.0

Semantic Web

See also

External links

References

  1. ↑ Halsal p. 359, 568
  2. ↑ Request for Comments: 3986, Uniform Resource Identifier (URI): Generic Syntax. IETF Network Working Group (January 2005). Retrieved on 2007-04-02.
  3. ↑ Request for Comments: 1945, Hypertext Transfer Protocol -- HTTP/1.0. IETF Network Working Group (May 1996). Retrieved on 2007-04-02.
  4. ↑ HTML 3.2 Reference Specification. World Wide Web Consortium (W3C) (14-Jan-1997). Retrieved on 2007-04-02.
  5. ↑ For historical reasons, the URI (Uniform Resource Identifier) is often referred to as the URL (Uniform Resource Locator), however this is not always the correct term to use - see URL#A popular synonym for "URI" for more information.
  6. ↑ RFC 2616. Uniform Resource Identifer (URI) Schemes. The Internet Society (1999). Retrieved on 2007-01-17.
  7. ↑ 7.0 7.1 Berners-Lee, Tim (1993/1994). A Brief History of the Web. World Wide Web Consortium. Retrieved on 2007-01-19.
  8. ↑ Template:Cite newsgroup
  9. ↑ Sturrock, Charles P.; Begle, Edwin F. (1995). Computerization and Networking of Materials Databases, Fourht Volume. ASTM International, 154. ISBN 0803120265. 
  10. ↑ CERN (1993-04-30). Statement concerning CERN W3 software release into public domain. Press release. Retrieved on 2007-01-19.
  11. ↑ Template:Cite newsgroup
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