The World Wide Web

What is the Web? Given the pace at which the Web has evolved, that is not an easy question to answer. I would say it is the universe of documents served by Web servers. A document can be a static file, like a simple HTML file, or a dynamic file whose content varies. Examples of dynamic content are a page that has stock quotes, one that displays the date, one customized for a specific client, or one with realtime streaming media. In more abstract terms, it is the universe of information linked together on the network by Web servers. In common usage we think of the underlying network as being the Internet.

The idea for the Web was conceived in 1989 by Tim Berners-Lee, and character based browsers were available as early as 1991. But in 1993, Marc Andreessen's Mosaic browser for X11 changed the way the Internet would be viewed, rendering hypertext documents with text styles, images, and links. That same year CERN granted the use of the WWW technology free of fees. In 1994 the World Wide Web Consortium was formed, to maintain and develop Web standards, and publish information about Web technologies. Their site is the best source of information about what makes the Web work.

One of the key principles of the Web, and the Internet, is openness. Contributors can collaborate and share information, and provide it in a way accessible to the widest possible audience. This calls for software interoperability, adherence to standards, and consideration of the needs of those with whom you wish to share this information. This could involve supporting many languages, character encodings, and customs. The presentation of the information might not be visual, or might be on a visual agent with limited capabilities. Observing standards, minimizing assumptions and dependencies, and common sense will help achieve such goals.

The URL

Each document on the Web is identified by its URL, Uniform Resource Locator. The term URI is also used, a URL is essentially a simple URI. The URL identifies the host on the network on which the document is located, what protocol to use to deliver it, and its name. Most documents use the http protocol. For example:

http://www.w3c.org/XML/Linking

The Web server at www.w3c.org will respond to an HTTP Request on its default port (80), and serve the file /XML/Linking from its filesystem, or equivalent database. A different port number can be requested by adding ":port" to the host identifier. A URL without the http prefix and host identifier will be interpreted relative to the current document. If that begins with a "/", it will be relative to the root of the server's virtual filesystem, or, with a file URL, relative to the root of your local filesystem.

HTML and XML

Generally, the resource so located will be a hypertext document written in a markup language, HTML, XML, or XHTML (a flavor of XML). In the early days, all documents were written in HTML (or plain text!), but as the needs and desires of the Web community grew, XML and XHTML were developed by the W3C. XML extended the family of structured documents in the Web paradigm. HTML was declared a type of document within that family, and newly dubbed as XHTML.

Dynamic content

The Web experience can be enhanced by the use of dynamic content. Web servers support CGI (Common Gateway Interface) scripts, and plugins, which can deliver customized content. Scripting languages, like JavaScript, and Web browser plugins can provide visual and audio effects, and help implement simple Web applications. They can also be distracting, when used gratuitously. Java applets allow a lightweight application to start in a web page frame, and escape the Web paridigm.

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• XML at OASIS
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