New Issues to Manage
Like anything else, the AJAX technique of partial data exchange can be misapplied so that server and network loads increase in an undesirable manner. So it's critical that AJAX developers are made aware of the importance of these issues and that bandwidth behavior is tested before applications are deployed.

Another concern is the misapplication of AJAX "push techniques," where AJAX toolkits enable servers to push incremental data to clients without requiring the clients to poll periodically. Developer education about these issues and pre-deployment testing of the application's network behavior are important.

With mashups plugging in third-party components there are potential security implications. It's recommended that IT managers establish a company policy on mashup products and technologies, such as only installing markup frameworks from trusted suppliers; only allowing components from trusted sources; and requiring secure gateway facilities that control the domains with which particular components can communicate.

Typically each AJAX toolkit has its own features, markup, and APIs. Long-term maintenance costs will be minimized if the application uses a popular Ajax toolkit that's familiar to a large pool of developers and by ensuring that the Ajax toolkit is OpenAjax-conformant. (See "Managing Long-Term Costs with Help from OpenAJAX.")

Other Factors To Consider
Now let's take a look at some additional key considerations in the cost/benefit analyses of adopting AJAX and determining ROI. Some important points to keep in mind include:

• Interaction and user experience requirements: If a given application requires either high levels of user responsiveness (that is, it's undesirable to use the old-style "click, wait, refresh" HTML technique) or requires a self-evident desktop-like user interface (to limit training costs) then AJAX techniques can reduce user wait time and improve productivity in a measurable way.
• Network bandwidth requirements: Applications that generate high levels of network activity often benefit from AJAX techniques by leveraging the partial data exchange and partial page update features associated with AJAX. AJAX techniques often replace full-page requests with small data exchanges, reducing network bandwidth requirements, minimizing server CPU processing, and improving response times.
• Scalability requirements: Large and/or growing user populations require scalable application deployment architectures. In such scenarios, it's critical to determine whether the AJAX-enabled application offers appropriate scalability characteristics.
• The mission-critical nature of the application: The greater the strategic value of the application, the greater the investment in RAS (reliability, availability, serviceability) required. Highly mission-critical applications may be less desirable early candidates, but offer the highest ultimate return.
• The complexity of database interaction: AJAX will be more difficult to apply where there's no good separation of back-end databases from the Web-tier application logic. Relevant questions to consider: Is the application tightly coupled to a back-end database? To what degree is transaction integrity and recoverability critical, and how do these factors relate to AJAX partial update techniques?
• The real-time nature of the underlying application: In general real-time monitoring and real-time business applications benefit significantly from AJAX, particularly the push technologies available in some AJAX toolkits.
• Systems integrator requirements: If the application requires involving a systems integrator then it's important to determine how familiar the integrator is with AJAX and the AJAX toolkits that you plan to use on the project.

Conclusion
The move to AJAX is part of a business operations strategy and is often coupled with the move to SOA. Arriving at estimates of return on AJAX or SOA is a difficult challenge for IT managers and executives. IT can support and even lead the effort by providing recommendations on appropriate questions to ask the business side of the house. IT can also help generate the answers needed to estimate ROI. Establishing an IT-user team to help the business drive the direction of the AJAX effort can be a forum for confirming and refining ROI estimates. Making the leap to AJAX isn't something that can be done overnight or with the snap of your fingers. It involves serious consideration and an honest internal evaluation. But by taking all of these points into account, decision makers will be better equipped to pave the way toward AJAX adoption.