Hi,
I was discussing this topic with Emmanuel Bernard by email and Emmanuel suggested that we move this conversation on the forum, so here we are :).

The idea would be to propose a javascript export of the bean validation rules.
Here is my point: when JSR303 came, it was quickly adopted by several major web frameworks/standards (such as JSF and Spring MVC). I'm sure that providing a Javascript export of the validation rules would help those frameworks to do "true client side validation".
Of course this could be implemented on the web framework side like it was the case for Rich-Faces. But in that case, we will need to reinvent the wheel for each framework.
Also, I'm not sure if it should be part of bean validation from the beginning. May be it would make more sense to make it part of Hibernate Validator until the JS code is considered as stable enough?

Currently there's a solution named " HOCON ", it seems promising to use the validation rules in end to end.
Please check yourself for specification and implementation.
github.com/typesafehub/config/blob/master/HOCON.md
github.com/deephacks/confit
marcinkubala.wordpress.com/2013/10/09/typesace-config-hocon/