Here is general requirements:
- the dependency shall be implemented in declarative form (settings, mapping, xml...)
- the displaying of the next control shall be dependent on input of previous control(s)
- one-to-one, one-to-many dependencies support
- actions (show, hide, disable, set value...) on depended controls.
- ajax calls
It is too complicated requirements and its can be simplified, but depended controls should be present.
I think, it can be useful, because everyone meet so stuffs in their UI.