This Programming Model seems to be very expressive. As far as I know JMatter is the first professional implementation, that provides persistency in a database as well as a rather nice UI and a useful set of base classes.
In the documentation there’s a chapter on the desktop, which describes the author’s vision of a desktop of objects. I think the consquences of applications beeing deployed as a set of classes into an objectframework are quite amazing. It reminded me of Dan Ingalls Byte article on the Design Principles Behind Smalltalk, where he argues that there shouldn’t be an operating system, which goes beyond the object runtime. He states: “An operating system is a collection of things that don’t fit into a language. There shouldn’t be one.”
Another interesting implication is the fact that JMatter provides a dramatic productivity boost which will lead to severe problems for those teams building everything from scratch. On the other hand new applications will become feasible due to falling prices.
There’s a lucid post by John Reynold’s.
I think this thing goes well beyond the scope of ruby on rails. Though it’s somewhat more complex due to the more static nature of the java language.