Solid Ajax Applications, Part 2: Building Ajax Back Ends
http://www-128.ibm.com/developerworks/views/web/libraryview.jsp?type_by=Articles

McLaughlin, Brett D.
IBM
2008

Abstract:

Back end processing -- server-side scripts and programs -- can't always be tossed into an Ajax application and behave well. Instead, careful planning to ensure data is sent in an appropriate and efficient form ensures your entire application is cohesive, rather than needlessly complex. Brett McLaughlin explains how a good server-side script complements Ajax behavior.