Forms engine

Hi All,

I have to provide to end user of my application possibility to create his/her own forms with validations (errors, warnings) and calculations without a need to rebuild/redeploy/restart the whole application. Key requirement is that it has to have graphical GUI for building forms (easy to use for no-programmer - drag and drop of form elements, clicking instead of typing, etc.). I should be able to pick up submitted form's result via web service (REST/SOAP) or it could be stored directly in database table.

Do you now any framework/solution which can (even partially) support me? I did research and for now I have two options: xforms (Orbeon) or do it from scratch. Any other options out there?