Adobe's Flex provides a way to push XML-based "code" from a server into a Flash player running on the browser. There's a nice online demo. It looks like a useful approach - the Flash player is nearly ubiquitous by now.

I can't help but think that the Tk browser plugin could have filled this spot ages ago. And much more, by now.

The news is that Flex will be open sourced before the end of the year. Think about it: open source code, written for a presentation engine that is fully controlled by Adobe. Clever. It's not easy to come up with scenario's whereby you get to lock-in open source developments.

In other words: to conquer the world, get into the browser. JavaScript and Flash did. Is everything else becoming irrelevant?

Update: another player in this field is Microsoft with Silverlight.