Ramdhan points to Isomorphic Software’s solution which translates to “Rich client + Thin client = Isomorphic SmartClient”:
Isomorphic SmartClient (ISC) brings the speed and functionality of desktop applications to standard web browsers. The ISC presentation layer is the first web application framework that spans across client and server, enabling live transactions and rich GUI interactivity without page reloads. ISC provides an easy, declarative authoring style for rapid development in either XML or JavaScript. And with a client-side system built upon standard browser technologies, ISC enables true zero-install applications.
Looks interesting. Try the test drive.