Modules and Wholes

User Acceptance Testing -- determining how well a system performs functionally -- should not be confused with Usability Testing -- determining how well a system meets user needs. Geeks fixate on technical performance, while usability advocates focus on human performance in the context of technical systems. But now that usability specialists have established what's important is not the system, it's the user, it seems this distinction is getting blurred again.

Enter Ajax. I've been slogging through some detailed writings on Ajax technology recently in a effort to catch up with the buzz. While only half understanding it all, I see indications that technical implementation is the difference between a positive or negative user experience. Paper prototyping is useless for Ajax. Forget how Ajax works in theory, worry about how it works in practice. Getting a browser to steal a moment to request data from a server takes some programming finesse, dealing with subtle timings on both client and server ends. JavaScript would seem especially unruly, given that it lacks the disciplinary structure of other programming languages and is prone to memory leaks. There seems ample possibilities for conflicts and hang-ups, which can grind user sessions to a slow march. I wonder if and when we will start seeing bad Ajax apps appearing on the net.

The more invasive web technologies become, downloading themselves onto a user's PC and affecting a user's memory resources, the more important live tests will become.