SitePoint’s PHP Blog (of all places):

AJAX is used to enhance existing HTML forms / user interaction but the fundamental paradigm is still the same as “normal” web applications. Some key smells of this style;

1. Page reloads still happen frequently
2. It’s possible (if you make the effort) to degrade gracefully to non-supporting browsers / browsers with JS turned off.
3. Session state still resides on the server.

Some of the key smells with Client / SOA;

1. Page reloads are rare, if at all. The application tends to run in a single browser window.
2. It’s practically impossible to degrade gracefully, without maintaining seperate code bases.
3. Session state is largely handled by the client.
4. Javascript and the browser are acting as a runtime in the same sense as the Java or .NET runtime.
5. It’s going to require specialist developers

Most people reading this have probably had some experience with Gmail, so you know that it fits in the first category above (now known as HTML++).

I took a free trial month with Mvelopes, and while I couldn’t justify the $8/month for their program (not when I’ve got Yodlee), it was good just to see what kind of things are possible in the world of “Client/SOA” web applications. We’re going to have to come up with a better name for that, right? Yeah. I would recommend that web developers (not so much the designers as the developers) take a look at it. The free trial is surprisingly easy to cancel when you’ve checked it out.

I think probably the most interesting thing above is the statement that Javascript and the browser acts as the run time environment. Are we going to see a JavaScript Enterprise Edition in a few years? Or is it more likely that people will find a better way to combine the Java or .NET run times with AJAX and/or DHTML and/or HTML++? AjaxFaces, anyone?