Folks, I am starting work on an iPad/iPhone application that is essentially a form-filing UI. The requirement is to present a (rather large) form to the user. The form is composed of sections and questions, like so:

• Form
  • Question 0.1
  • Question 0.2
  • Section 1
  • Question 1.1

etc.

The user can take various paths down the form based on answers to questions.

I would like to architect this by defining a declarative markup that can be used to author the form questionnaire including traversal rules.

My questions are:

• Can anyone recommend a markup/language that would satisfy the declaration requirement?
• Is there any existing library that would ease the implementation as described above?

Thanks for your time.