   #copyright

World Wide Web

2007 Schools Wikipedia Selection. Related subjects: Websites and the Internet

   WWW's historical logo designed by Robert Cailliau
   Enlarge
   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 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.

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;
     * 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. Polly is famous as " NetMom" in the history of the Internet.

   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.

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, graphics and any other files that form a part of
   the page will be requested and returned to the client (the Web browser)
   in quick succession.

   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 .

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 expiry 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.

Origins

          See also: History of the Internet - CERN, Where the Web Was
          "WWW" born

   This NeXTcube used by Berners-Lee at CERN became the first Web server.
   Enlarge
   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 :
   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 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
   Centre 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.

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.

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.

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.

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.

Statistics

   According to a 2001 study, there were more than 550 billion documents
   on the Web, mostly in the " invisible Web". A 2002 survey of 2,024
   million Web pages 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.

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.

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.

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.

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" and even today many Web sites
   are available without the "www" prefix.

   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".

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".

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.

Standards

   The following is a cursory list of the documents that define the World
   Wide Web's three core standards:
     * Uniform Resource Locators (URL)
          + RFC 1738, Uniform Resource Locators (URL) (December 1994)
          + RFC 3986, Uniform Resource Identifier (URI): Generic Syntax
            (January 2005)
     * HyperText Transfer Protocol (HTTP)
          + RFC 1945, HTTP/1.0 specification (May 1996)
          + RFC 2616, HTTP/1.1 specification (June 1999)
          + RFC 2617, HTTP Authentication
          + HTTP/1.1 specification errata
     * Hypertext Markup Language (HTML)
          + Internet Draft, HTML version 1
          + RFC 1866, HTML version 2.0
          + HTML 3.2 Reference Specification
          + HTML 4.01 Specification
          + Extensible HTML (XHTML) Specification

   Retrieved from " http://en.wikipedia.org/wiki/World_Wide_Web"
   This reference article is mainly selected from the English Wikipedia
   with only minor checks and changes (see www.wikipedia.org for details
   of authors and sources) and is available under the GNU Free
   Documentation License. See also our Disclaimer.
