World Wide Web
From Hill2dot0
Contents |
The Beginning
Tim Berners-Lee is considered by many to be the “Father of the WWW.” A physicist by training, he worked in the computer and telecommunications industries following graduation from Oxford, and eventually accepted a consulting position as a software engineer with the European Center for Nuclear Research (CERN) during the late 1970s.
During his stint in Geneva, Berners-Lee observed that CERN suffers from the problems that plague most major organizations: information location, management, and retrieval. CERN is a research organization with large numbers of simultaneous ongoing projects, a plethora of internally published documentation, and significant turnover of people. As a consequence, Berners-Lee found that his ability to quickly locate and retrieve a particular piece of information was seriously impaired by the lack of a single common search capability. To satisfy this need, in 1980 he wrote a search and archive program called Enquire. Enquire was never published as a product, although both Berners-Lee and the CERN staff used it extensively. In fact, it proved to be the foundation for the World Wide Web.
In May 1990, Berners-Lee published Information Management: A Proposal, in which he described his experiences with hypertext systems and the rationale for Enquire. He described the system’s layout, feel, and function as being similar to Apple’s Hypercard, or the old “Adventure” game where players went from “page to page” as they moved through the game. Enquire had no graphics, and was rudimentary compared to modern Web browsers, but it did run on a multiuser system and could therefore be accessed simultaneously by multiple users.
In November 1990, Berners-Lee wrote and published, with Robert Cailliau, Worldwide Web: A Proposal for a Hypertext Project. In it, the authors describe an information retrieval system in which large and diverse compendiums of information could be searched, accessed, and reviewed freely using a standard user interface based on an open, platform-independent design. This paper relied heavily on Berners-Lee’s earlier publication, Information Management: A Proposal. In this second paper, Berners-Lee proposed the creation of a “worldwide web” of information that would allow the dispersed CERN entities to access the information they need, based on a common and universal set of protocols, file exchange formats, and keyword indices. The system would also serve as a central (although architecturally distributed) repository of information, and would be totally platform-independent. Furthermore, the software would be available to all and distributed free of charge.
After Berners-Lee’s second paper, Worldwide Web: A Proposal for a Hypertext Project, had been circulated for a time, the development of what we know today as the World Wide Web (WWW) occurred with remarkable speed. The first “system” was developed on a NeXT platform. The first general release of the WWW inside CERN occurred in May 1991, and in December the world was notified of the existence of the World Wide Web (known then as W3) thanks to an article in the CERN computer newsletter. Over the course of the next few months, browsers began to emerge. Erwise, a graphical user interface (GUI) client, was announced in Finland, and Viola was released in 1992 by Pei Wei of O’Reilly & Associates. NCSA joined the W3 consortium, but didn’t announce their Mosaic browser until February 1993.
The Growth Period
Throughout all of this development activity, W3 servers, based on the newly released HyperText Transfer Protocol (HTTP) that allows diverse sites to exchange information, continued to proliferate. By January of 1993, there were 50 known HTTP servers; by October there were over 200 and WWW traffic comprised one percent of aggregate National Science Foundation (NSF) backbone traffic. The juggernaut had begun.
In May 1994, the first international WWW conference was held at CERN in Geneva, and from that point on they were organized routinely, always to packed houses and always with a disappointed cadre of oversubscribed would-be attendees left out in the cold.
From that point on, the lines that clearly define “what happened when” begin to blur. NCSA’s Mosaic product, developed largely by Marc Andreessen at the University of Illinois in Urbana-Champaign, hit the mainstream and brought the World Wide Web to the masses. Andreessen, together with Jim Clark, would go on to found Netscape Corporation shortly thereafter.
And today? Today, the World Wide Web is much more than a technology. It is a world, a culture, and a massive vertical industry that provides form and sustenance to countless dependent sub-industries.
World Wide Web Anatomy
The visual illustrates the relationships between the WWW components. In a typical session, four key events take place.
- The Web browser opens a connection at the appropriate IP address/port number.
- The client sends a request to the server, detailing the method HTTP will use to carry out the requested transaction.
- The server sends the requested information to the client.
- The server closes the logical connection.
World Wide Web Components
The World Wide Web (WWW) consists of four principal components: Uniform Resource Locators (URL), HyperText Markup Language (HTML); HTTP and HTTP client/server transactions, and resource processing, which is generally carried out on the server using the Common Gateway Interface (CGI).
URLs represent the standard addressing scheme utilized on the WWW to specify the location of information on the Web. An example showing standard URL format is shown below. http://www.hill.com
Here, http:// indicates that the HTTP will be used to transfer information from a World Wide Web server (www.) located at a site called ‘hill,’ that happens to be in the commercial (.com) domain.
HTML is the “programming language” used to format documents in a universal, standardized format so they can be downloaded from a Web server as hypertext documents. The markup language consists of formatting commands that allow a user to specify, among other things, the location, size, color, alignment, and spacing of headings, full-text paragraphs, animation sequences, quotations, and images on a page, as well as functional “buttons” that lead to other hypertext documents. Like all resources on the World Wide Web, the location of these documents is specified through a URL. These URLs can point not only to text, but also movie clips, image files, music, and so on. If the information can be digitized and stored on a hard drive or CD-ROM, it can be pointed to with a URL using HTML formatting and downloaded to the requesting system using the HTTP.
HTTP lies at the heart of the World Wide Web. It represents the command syntax used to transfer documents from a Web server to a Web client, similar to the File Transfer Protocol (FTP). In fact, HTTP is a client/server environment. Transactions are carried out between the client and the server, moving the requested file from the server to the client.
CGI is a standard way for a Web server to pass a user’s request on to an application program, which then handles the request. Database Interface (DBI) provides the means for the Web server to receive the results from the application so that it can pass the results back to the requesting user.
Applications and Capabilities of the Web
Web applications and capabilities include Java, ActiveX, RealAudio, RealVideo, the Virtual Reality Modeling Language (VRML), XML, Shockwave, and a host of others. Most of these employ an HTML element called EMBED and are designed to do one of two things: either embed formatting information (objects) within an HTML document for special forms of data (e.g., images, sounds, or movies), or embed executable mini-applications in the same document, such as Java Applets or Microsoft ActiveX files. Browser plug-ins, “helper applications” that help format and present the data on-screen, are often required to view objects and are sometimes quite large (i.e., require significant system resources).
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