Using a declarative DSL designed for validation rules should make it much simpler, it would minimize the amount of writing the boilerplate stuff that comes with

Using a declarative DSL designed for validation rules should make it much simpler, it would minimize the amount of writing the boilerplate stuff that comes with a general purpose language and would focus solely on the actual validation rules. It could be used in the same way as templating for javascript is used, a script element with a custom type or validation-src attribute in the form or something.