the view is important

I have been developing web applications for only 4 years but this has
been enough to know that HTML+CSS+Javascript is the hardest part.
Nowadays there exists many javascript libraries such as jQuery and
some javascript frameworks such as Ext. But, as you may know, they are
very hard to use to create a fully integrated RIA.
To solve this, there are presentation frameworks that centers the
development on the server. Examples of such that frameworks are ZK
(based on jQuery) and Vaadin (based on GWT). All of this examples use
Java EE, not RoR.
Is someone developing any server-centric presentation framework?

Pau wrote:

I have been developing web applications for only 4 years but this has
been enough to know that HTML+CSS+Javascript is the hardest part.
Nowadays there exists many javascript libraries such as jQuery and
some javascript frameworks such as Ext. But, as you may know, they are
very hard to use to create a fully integrated RIA.
To solve this, there are presentation frameworks that centers the
development on the server. Examples of such that frameworks are ZK
(based on jQuery) and Vaadin (based on GWT). All of this examples use
Java EE, not RoR.
Is someone developing any server-centric presentation framework?

These frameworks you mentioned (jQuery, GWT, etc.) are not at all
server-centric. They are client-side JavaScript frameworks. What you use
on the server side should make no difference. Granted some of these may
assume Java EE on the server-side, but I even doubt that.

There are also some other options you didn't mention. I know for sure
that these make no assumptions about what you're running server-side.

http://cappuccino.org/
http://www.sproutcore.com/