WWW: World Wide Web

The World Wide Web (WWW, W3, or the Web) provides a unified, interconnected interface to the vast amount of information stored on computers around the world. The idea that spawned the World Wide Web came from the mind of Tim Berners-Lee (www.w3.org/People/Berners-Lee) of the European Particle Physics Laboratory (CERN) in response to a need to improve communications throughout the high-energy physics community. The first-generation solution consisted of a notebook program named Enquire, short for Enquire Within Upon Everything (the name of a book from Berners-Lee's childhood), which he created in 1980 on a NeXT computer and which supported links between named nodes. Not until 1989 was the concept proposed as a global hypertext project to be known as the World Wide Web. In 1990, Berners-Lee wrote a proposal for a hypertext project, which eventually produced HTML (Hypertext Markup Language), the common language of the Web. The World Wide Web program became available on the Internet in the summer of 1991. By designing the tools to work with existing protocols, such as FTP and gopher, the researchers who created the Web produced a system that is generally useful for many types of information and across many types of hardware and operating systems.

The WWW is another example of the client/server paradigm. You use a WWW client application, or browser, to retrieve and display information stored on a server that may be located anywhere on your local network or the Internet. WWW clients can interact with many types of servers. For example, you can use a WWW client to contact a remote FTP server and display the list of files it offers for anonymous FTP. Most commonly you use a WWW client to contact a WWW server, which offers support for the special features of the World Wide Web that are described in the remainder of this chapter.

The power of the Web derives from its use of hypertext, a way to navigate through information by following cross-references (called links) from one piece of information to another. To use the Web effectively, you need to run interactive network applications. The first GUI for browsing the Web was a tool named Mosaic, which was released in February 1993. Designed at the National Center for Supercomputer Applications at the University of Illinois, its introduction sparked a dramatic increase in the number of users of the World Wide Web. Marc Andreessen, who participated in the Mosaic project at the University of Illinois, later cofounded Netscape Communications with the founder of Silicon Graphics, Jim Clark. The pair created Netscape Navigator, a Web client program that was designed to perform better and support more features than the Mosaic browser. Netscape Navigator has enjoyed immense success and has become a popular choice for exploring the World Wide Web. Important for Linux users is the fact that from its inception Netscape has provided versions of its tools that run on Linux. Also, Netscape created Mozilla (mozilla.org) as an open-source browser project.

These browsers provide GUIs that allow you to listen to sounds, watch Web events or live news reports, and display pictures as well as text, giving you access to hypermedia. A picture on your screen may be a link to more detailed, nonverbal information, such as a copy of the same picture at a higher resolution or a short animation. If your system can produce audio output, you can listen to audio clips that have been linked to a document.

URL: Uniform Resource Locator

Consider the URL http://www.w3.org/Consortium/siteindex. The first component in the URL indicates the type of resource, in this case http (HTTPHypertext Transfer Protocol). Other valid resource names, such as https (HTTPSsecure HTTP) and ftp (FTPFile Transfer Protocol), represent information available on the Web using other protocols. Next come a colon and double slash (://). Frequently the http:// string is omitted from a URL in print, as you seldom need to enter it to reach the URL. The next element is the full name of the host that acts as the server for the information (www.w3.org/). The rest of the URL consists of a relative pathname to the file that contains the information (Consortium/siteindex). If you enter a URL in the location bar of a Web browser, the Web server returns the page, frequently an HTML (page 1036) file, pointed to by this URL.

By convention many sites identify their WWW servers by prefixing a host or domain name with www. For example, you can reach the Web server at the New Jersey Institute of Technology at www.njit.edu. When you use a browser to explore the World Wide Web, you may never need to enter a URL. However, as more information is published in hypertext form, you cannot help but find URLs everywherenot just online in email messages and Usenet articles, but also in newspapers, in advertisements, and on product labels.

Browsers

Mozilla (www.mozilla.org) is the open-source counterpart to Netscape. Mozilla, which was first released in March 1998, was based on Netscape 4 code. Since then, Mozilla has been under continuous development by employees of Netscape (now a division of AOL), Red Hat, and other companies and by contributors from the community. Firefox is the Web browser component of Mozilla. KDE offers Konqueror, an all-purpose file manager and Web browser (page 94). Other browsers include Epiphany (www.gnome.org/projects/epiphany) and Opera (www.opera.com). Although each Web browser is unique, all of them allow you to move about the Internet, viewing HTML documents, listening to sounds, and retrieving files. If you do not use the X Window System, try a text browser, such as lynx or links. The lynx browser works well with Braille terminals.

Search Engines

Search engine is a name that applies to a group of hardware and software tools that help you search for World Wide Web sites that contain specific information. A search engine relies on a database of information collected by a Web crawler, a program that regularly looks through the millions of pages that make up the World Wide Web. A search engine must also have a way of collating the information the Web crawler collects so that you can access it quickly, easily, and in a manner that makes it most useful to you. This part of the search engine, called an index, allows you to search for a word, a group of words, or a concept; it returns the URLs of Web pages that pertain to what you are searching for. Many different types of search engines are available on the Internet, each with its own set of strengths and weaknesses.