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 of the European Particle Physics Laboratory (CERN) in response to a need to improve communications throughout the High Energy Physics community. The first generation was 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 provided for links to be made between named nodes. It was not until 1989 that the concept was 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 created a system that is generally useful for many types of information and across various 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 be able to run interactive network applications. The first GUI for browsing the Web was a tool named Mosaic, which was released in February 1993. It was designed at the National Center for Supercomputer Applications at the University of Illinois and 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. They 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 users exploring the World Wide Web. Important for Mac OS X users is the fact that from the beginning Netscape has provided versions of its tools that run on the Mac. Also, Netscape created Mozilla (mozilla.org) as an open-source browser project. Apple's Safari browser is based on Konqueror's (www.konqueror.org) rendering engine, the code used to display Web pages.
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/pub/WWW. 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 comes a colon and double slash (://). Frequently the http:// string is omitted from a URL in print, as you seldom need to enter it to get to the URL. Following this is the full name of the host that acts as the server for the information (www.w3.org/). The rest of the URL is a relative pathname to the file that contains the information (pub/WWW). Enter a URL in the location bar text box of a Web browser, and the Web server returns the page, frequently an HTML (page 936) 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 use a URL directly. 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.
Most Macintosh users are familiar with Apple's Safari Web browser. Mozilla, Firefox, Opera, and several other browsers are also available for free. In addition, you can purchase commercial browsers, such as OmniWeb (www.omnigroup.com), that will run under OS X.
Search engine is a name that applies to a group of hardware and software tools that help you find World Wide Web sites that have the specific information you are looking for. 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 and 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.