Three Protocols, the

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THREE PROTOCOLS, THE

The World Wide Web is one of several utilities—including e-mail, File Transfer Protocol (FTP), Internet Relay Chat (IRC), Telnet, and Usenet—that form the Internet. At the heart of the Web is a system of many Web servers. While the term server is normally used to describe the computers that host Web sites, it also can refer to the software used to store Web pages. The World Wide Web Consortium (W3C) describes the Web as "the universe of network-accessible information, the embodiment of human knowledge." This statement describes the vision of the Web's creator, a computer scientist named Tim Berners-Lee, who developed three critical protocols that make it work.

WHY THE WEB WORKS

The three protocols Berners-Lee developed are Hypertext Markup Language (HTML), Uniform Resource Locator (URL), and Hypertext Transfer Protocol (HTTP). Protocols are formats or sets of rules that computers use when they communicate. Residing either in software or hardware, they ensure that each device understands exactly how information will be sent and received.

Locations on the World Wide Web, which commonly reside on individual servers, are known as Web sites. Web sites have individual addresses called URLs, which must be used to gain access. Much like a street address or telephone number is linked to a person or company, URLs are linked to Web sites. Originally, URLs were called Universal Document Identifiers (UDIs) or Uniform Resource Identifiers (URIs).

Upon visiting a Web site, visitors normally begin on the site's home page. This document serves as an index to other pages or documents within the site, which are written in a language called HTML—an authoring or presentation language (not a programming language) used for creating pages on the World Wide Web. The HTML language consists of special codes or tags that determine a page's visible appearance when read by a Web browser like Microsoft's Internet Explorer. In addition to defining the overall structure and layout of a Web page, HTML also is used to denote links to other Web pages, the placement of graphics or pictures on a page, and the appearance of text, including bold or italicized type and different fonts.

HTML documents, or Web pages, are connected together with hypertext links. This linking is made possible by HTTP, a protocol used by computers to transfer hypertext documents and other chunks of information over the Internet. HTTP relies on a client-server model, similar to other protocols used on computer networks. In this scenario, clients are programs like Web browsers that interact with Web servers to request and retrieve information. As explained in HTTP Made Really Easy, "An HTTP client opens a connection and sends a request message to an HTTP server; the server then returns a response message, usually containing the resource that was requested. After delivering the response, the server closes the connection (making HTTP a stateless protocol, i.e. not maintaining any connection information between transactions)."

Web pages are viewed through software applications called Web browsers. Microsoft's Internet Explorer and Netscape's Navigator were the two popular Web browsers during the 1990s and early 2000s. Web browsers are the essential link between end-users and a vast sea of static pictures, video, sounds and text. Said differently, they also enable buyers and sellers of goods and services to engage in electronic commerce.

HOW IT ALL HAPPENED

In 1980, shortly after graduating from Oxford University, Tim Berners-Lee held a temporary software consulting job at the European Particle Physics Laboratory (CERN). There, he experimented with programs, including one called Enquire, which stored information along with links. He developed Enquire as a way of helping himself remember connections between the many people and projects at CERN. After his temporary position ended, Berners-Lee eventually returned to CERN in a more permanent role in 1984. He had a vision of a "global information space" where information on computers throughout the world was linked together. Many of the researchers who worked with CERN were scattered throughout the world. CERN made them submit documents in a special format that was compatible with its own computer system. This caused a great deal of frustration, both for the researchers and the people who were employed at CERN. Consistent with his vision, Berners-Lee proposed creating a web of information that would be in a universal format all could share. This web could contain cross-links between relevant documents, such as research papers. Although the idea generated little initial interest at CERN, Berners-Lee's boss, Mike Sendall, gave him permission to explore his dream there. In response, he created a hypertext-editing program called WorldWideWeb in 1990. The program ran on a machine from NeXT, a computer company started by Apple co-founder Steve Jobs, and included the Web's three main elements—URLs, HTTP, and HTML—which Berners-Lee created.

The concept of hypertext existed long before Berners-Lee introduced HTTP and HTML. During the 1940s, the concept existed in the academic world. Also, during the 1980s, Apple Computer Programmer Bill Atkinson created a program called Hypercard. According to WC3, the program allowed users "to construct a series of on-screen 'filing cards' that contained textual and graphical information. Users could navigate these by pressing on-screen buttons, taking themselves on a tour of the information in the process. Hypercard set the scene for more applications based on the filing card idea." One limitation to programs like Hypercard was that they were limited to a person's computer system and couldn't be used to access information on other computers or networks in remote locations.

Berners-Lee introduced his WorldWideWeb program, along with the very first Web server (called info.cern.ch), to people in the field of high-energy physics. Later, he introduced WorldWideWeb to people introduced in hypertext and NeXT. At info.cern.ch, the specifications for URLs, HTML, and HTTP were published in order to encourage others to learn about and use them.

After Berner-Lee introduced his creation to the world, it began to take off. However, the browser he made for NeXT was not sufficient for the many people using IBM-PCs, Macintosh computers, and other systems. Development of various point-and-click browsers soon followed. According to ibiblio, "Students at the Helsinki University of Technology wrote Erwise-a browser for Unix machines, and Pei Wei, a U.C. Berkeley student wrote Viola. Colleagues of Berners-Lee at CERN wrote a browser for Mac machines called Samba." In 1992, Dave Thompson and Joseph Hardin of the University of Illinois at Champaign-Urbana's National Center for Supercomputer Applications decided to develop the Mosaic Web browser. Lou Montulli was among the first people to create a text browser, when he released Lynx in March of 1993. That same year, Hewlett-Packard Labs' Dave Raggett created a browser called Arena. In November 1994, Marc Andreessen, who had worked as a programmer on Mosaic, and Jim Clark formed what would eventually become Netscape Communications. Microsoft released its Internet Explorer browser in August of 1995, and along with Netscape went on to dominate the market for Web browsers.

Since Berners-Lee effectively changed the world, the Web has evolved. For example, various versions of HTML, including HTML+, HTML 2, HTML 3.2, HTML 4, have been released. HTML is closely related to another language called Standard Generalized Markup Language (SGML). In the early 2000s a subset of SGML known as Extensible Mark-up Language (XML) led to the development of XHTML, a hybrid language that combines HTML with XML. XHTML has powerful implications for e-commerce because the language's XML component allows users to share information in a universal, standard way without making the kinds of special arrangements required Electronic Data Interchange (EDI), or the manner in which many large companies exchange electronic data with suppliers and other entities.