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Rich client, Poor client, Cool client, Ajax
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04/12/2006, By Joe Winchester
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Asynchronous Java Script and XML, shortened to Ajax , is the flared technology de-jour. Like fashion, cooking, or music it’s a mix of stuff that’s old, borrowed, and not that new. It does exactly what it says on the tin, mixing Java Script on the browser with async XML traffic.
The problem with the web has always been that despite anyone trying to convince you otherwise, it’s a page based latency bound transaction model that is a dressed up graphical mainframe. Works well because the transport protocol is neutral and ubiquitous allowing heterogeneous end points where the client and server don’t have to know all that much about each other, just how to establish an HTTP connection. Problem with web is that if all the logic occurs on the server back end app, then the client is relegated to being just a dumb renderer of HTML, which sort of belittles the fact that PCs are pre-emptive multi-tasking box with oodles of processing power.
Java Script has always been a sensible way to try to reduce server round trips where client side validation or other logic can be performed, and also to butter up the GUI with dialogs and other user interface experiences above the lowest common denominator of HTML. The latency problem however has typically remained where each page’s unit of work is completed by despatching a request to the server with the data and a new page dispatched. What makes Ajax clever though is that it keeps the HTTP transaction alive and uses it to perform fine grained requests during the lifetime of the page, and doing this asynchronously by having the browser’s Java Script communicate with the server doesn’t detract from the client’s responsiveness. It also removes the whole web experience feeling where waiting for the result of an HTTP communication is usually coincident with having to wait for a new page and the whole experience goes into a synchronous busy wait.
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