A Short History of the Web

In the late 1950s, the U.S. government formed the Advanced Research Projects Agency (ARPA). This was largely a response to the Russian success in launching the Sputnik satellite and employed some of the country's top scientific intellects in research work with U.S. military applications.

During the 1960s, the agency created a decentralized computer network known as ARPAnet. This embryonic network initially linked four computers located at the University of California at Los Angeles, Stanford Research Institute, the University of California at Santa Barbara, and the University of Utah, with more nodes added in the early 1970s.

The network had initially been designed using the then-new technology of packet switching and was intended as a communication system that would remain functional even if some nodes should be destroyed by a nuclear attack.

Email was implemented in 1972, closely followed by the telnet protocol for logging on to remote computers and the File Transfer Protocol (FTP), enabling file transfer between computers.

This developing network was enhanced further in subsequent years with improvements to many facets of its protocols and tools. However, it was not until 1989 when Tim Berners-Lee and his colleagues at the European particle physics laboratory CERN (Conseil Européen pour le Recherche Nucléaire) proposed the concept of linking documents with hypertext that the now familiar World Wide Web began to take shape. The year 1993 saw the introduction of Mosaic, the first graphical web browser and forerunner of the famous Netscape Navigator.

The use of hypertext pages and hyperlinks helped to define the page-based interface model that we still regard as the norm for web applications today.

The XML DOM

The XML Document Object Model defines a standard way for accessing and manipulating XML documents. The DOM enables JavaScript to completely access XML or XHTML documents by providing access to the elements which define the structure. The accessibility is possible through a set of intrinsic JavaScript objects that focus on DOM manipulation. This model is something that we will be using throughout the rest of this book because it is required to parse the responses that we receive from the server side when we create an XMLHTTPRequest (XHR). As mentioned earlier, the XHR is the core of the Ajax model and without it the model would not exist. This is the piece of the Ajax puzzle that has created the recent buzz because it allows HTTP requests to be made to the server without refreshing the browser.

Though there has been a lot of recent hype surrounding Ajax, it has existed for quite some time. Microsoft originally released the XHR object in 1999 with Windows IE 5 as an ActiveX object available through the use of JavaScript and VBScript. It is now supported by Mozilla, Firefox, Safari, Opera, and Netscape by using a native JavaScript object. This native JavaScript object will also be supported with the release of Windows Internet Explorer (IE) 7. Although the technologies have been in existence and used by some developers in the past, it has only recently gained large popularity. The cause of its recent popularity is largely based on the support that is offered by browsers because not many browsers had the support necessary for powerful DHTML, XHTML, CSS, and XMLHTTPRequests until more recent versions. Now it is possible to create such interactions with successful cross-browser and cross-platform results. The adoption of better support for these technologies has brought Ajax to the forefront and it is once again an exciting time to be a web developer. Small, independent operations are regularly emerging with applications that rival the desktop by providing powerful functionality while immensely improving the user experience.