What is the difference between Web 2.0, AJAX, and XHR
Frequently I hear even web developers getting this wrong, so I'm going to put my spin on it and hopefully everyone will understand what the differences are between Web 2.0, AJAX, and XmlHttpRequest.
I'll start with Web 2.0. First of all, if you are speaking in fact, probably the first Web 2.0 site was eBay. The way I define Web 2.0 is that a site has user driven content, and basically provides the medium to allow some behavior over the internet. Therefore sites like myspace, and facebook are Web 2.0, even thought they may or may not use AJAX or XmlHttpRequest. However, even before those sites, eBay embodied Web 2.0 in spirit as well as in fact. So really Web 2.0 is about companies partnering with users to provide good content. What that means is that perhaps the company provides some information, but users provide feedback, or they are enabled through some other method of communication / cooperation. So Web 2.0 really isn't about technology at all, it is more about a concept. Web 2.0 usually is delivered in conjunction with AJAX because AJAX provides a new way for users to interact with a site and get immediate feedback.
Lastly, we arrive at XmlHttpRequest, or XHR for short. Just because a site uses XHR does not make it AJAX, or Web 2.0. XHR was originally used to load Xml documents without having to make the page refresh, to give web sites easy access to information. To a degree, the current use of XHR is not very different from its original intended use. The real difference comes when it is used in conjunction with either or both the AJAX, and (or) Web 2.0 mindset.
What organizations need if they wish to start creating “Web 2.0” or “AJAX” sites is not really different engineers, what they really need is a change in the general perception or idea of what a web experience should be. They should understand that the idea of a “Web Site” is outdated. The really need to craft an experience. That means that it has to have a flow, be contextual, as well as being easy and simple. Building sites that conform to all of the buzzwords “AJAX”,”Web 2.0″, and “XHR” isn't easy. Probably the easiest part is the “XHR.” It really requires studying usability and excellent interface design. Fortunately I have been seeing an incredible willingness to learn and try to achieve these goals with the people whom I have recently been talking from different companies. Knowing that, I'd say that the Internet is just starting on its act 2, and that there is much more to come.