“When we were young, we were told that ‘Everybody else is doing it’ was a really stupid reason to do something. Now it’s the standard reason for picking a particular software package.” — Barry Gehm

When you make decisions, one strong bias is the bandwagon effect. The idea is that humans often do or think things just because many others do the same. Now, after convincing yourself that Ajax is something you have to use, be careful not to find artificial excuses to use it. To some people, Ajax is the latest proverbial hammer, and they will use any excuse to find themselves some suitable nails. Remember that Ajax is a tool, not a toy or purpose in itself.

With each new technology that is introduced, people like to experiment and test the tipping point. For instance, when color monitors first came out, a deluge of applications changed their fonts and colors as much as possible, just because they could. No user really wants a mouse trailer, yet a large number of Web designers seem to think that they have to add them to their sites. I feel that, if we’re not careful, the same phenomenon will happen with Ajax.

Ajax is also fueling a venture capital frenzy. The investment climate for technology startups seems to have become friendly again, and one of the magic keywords these days is Ajax. Collaboration-based startup Zimbraâ„¢, a heavy Ajax user, has already secured $16 million. Other startups are scrambling to claim that they are Ajax-based as a result, to sell more products or receive more attention from investors.

If you find yourself wanting to use Ajax, make a balanced decision about where exactly you think it makes sense, and where it does not.

Ajax lets Web developers create interactive Web sites that function more like desktop programs rather than static Web sites. Gmail and Google Maps are two of the most common examples of sites built using Ajax. A variety of techniques allow Ajax to place the interactivity directly within the browser, instead of the browser having to constantly contact a Web server to get information.

When someone visits an Ajax site, the browser loads the HTML page as it would normally. After that, though, Ajax uses JavaScript for interactivity. When a site visitor makes a request for more information — for example, to fetch a map — the JavaScript makes the request. The JavaScript doesn’t make a request for information directly to a Web site, though — instead, it uses an API called XMLHttpRequest to transfer the data back and forth. (The data requested is usually in XML format, although it doesn’t have to be.) This allows the Web page and JavaScript to continue to interact with the user, while the XMLHttpRequest handles communications with the server.

JavaScript takes the information handed to it by the XMLHttpRequest, and then uses it or displays it. But only the portion of the page that needs the information is refreshed. This speeds up the display of information, because the entire page doesn’t have to be changed.

Doing some recent research within the area of AJAX led me to a spin-off of the Ajax era of web application development called Comet. Using Comet, developers have the ability to stream data to and from the browser, instead of communication done thru series of call backs between the browser and the server. Seems like a slick idea, but if you have not used JSON before (basically a Java based XML language) you are in for a slight learning curve. Lingr.com is a great example of an easy use of Comet in the development of a web based chat room website, and is really quite slick. Meebo.com is also another good example. A good starting tutorial is also available here.