Rich Internet Applications are fast. When you click a button or push a lever, things tend to happen right away. That fast user experience is a primary reason that developers and designers are attracted to RIAs. Latency is reduced (after the initial download) for two reasons
1) Because the UI is inherently preloaded: it is not being shipped back and forth every time the user performs an act of navigation.
2) Because data can potentially be preloaded: the application can download data in the background that it thinks you will use, before you request it.
AJAX
Affordance and the API
Geeks spend a lot of time talking about what’s possible with a particular technology. We pride ourselves in being able to wring every drop of interactivity out of a platform, of doing things with the tools that the toolmakers never would have thought possible. As a result, any argument about software platforms often falls into the following pattern: Detractor of Platform A will say something like “you can’t do drag and drop in Platform A”. Supporter of Platform A will respond that you can so drag and drop in Platform A, and will post the code to prove it. Score one for the supporter: the detractor simply wasn’t able to use the tool.
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