The protocols for such services are often difficult to distinguish from line noise. Even if such services were not trying to make their protocols difficult to reverse-engineer, Jabber's would likely still be easier to work with because of its XML basis. Software which supports XML can easily handle supporting new XML document tyes, such as the Jabber protocol, and a raw dump of the traffic would look familiar to anyone who has built a web page: tag-based markup intended to be human-readable.
When the World Wide Web was new, many predicted that it would replace traditional desktop applications. Java applets were usually the means by which this was to happen, though in reality they have much in common with regular desktop applications. Using normal web pages as a user interface to an applications has significant disadvantages relative to a normal desktop application, most of which are related to the fact that the user must load a new page every time any significant interaction with the application occurs. Such page loads are inconvenient for users, and have discouraged the use of the web to replace traditional desktop applications. With the introduction of the Javascript XMLHttpRequest object, web application design has become more like the desktop.
XMLHttpRequest allows a web page to communicate with a server using XML. Javascript already had the ability to update content on an already-rendered page. The addition of the ability to communicate with a server means that web applications can truely start to behave more like desktop applications. The technique has been given a name: Asynchronous Javascript And XML, or Ajax, which has been widely adopted. (Garrett 2005) Writing an Ajax application involves significantly more complexity than a traditional web application, but has very large potential usability benifits for the user. For an Ajax application to work well, several elements are required: standards-compliant HTML and CSS, a client-side Ajax engine written in Javascript, and server-side processing to respond to the...
XML is used as the format for bi-directional communication between the web page and the server. Updates are made by the Javascript Ajax engine without having to reload the page, making for a much smoother user experience.
Ajax applications are more of a challenge to write than traditional static HTML web applications, but the reward in terms of attractiveness to the user can be significant. Ajax is the reason Google Maps, and MSN's clone thereof are so much more interactive than older mapping services such as Mapquest. Many users feel that Google's Ajax-based Gmail web interface is the first web-based email system to approach the level of usability offered by desktop mail client software. The ability to communicate asynchronously finally gives web applications the sort of real interactivity previously reserved for desktop programs.
XML provides developers with a standard format for programs to store and exchange data. Without a standard format for data interchange, much of the effort involved in developing a system that includes several programs is just getting them to talk to each other. There is nothing revolutionary about the XML format itself; it strongly resembles Lisp property lists, but with a more verbose syntax. What is revolutionary in the level of support for XML among software developers. With increasing frequency, programs are expected to "speak" XML, and as a result, can easily communicate with each other. With the communication barrier out of the way, information can flow freely between programs, allowing developers to create larger systems from them.
Garrett, J. (18 February, 2005) Ajax: A New Approach to Web Applications [online]. Available from: [30 July 2005].
Graham, P. (May 2002) Revenge of the Nerds [online]. Available from: [30 July 2005].
Jabber Technical Overview (26 January, 2005) [online]. Available from: [30 July 2005].
Raymond, E. (19 September, 2005) The Art of Unix Programming [online]. Available from: [30 July 2005].
