I am trying to create a grid form for a survey question.

            value1     value2   value3

option 1      x

option 2                 x

option 3      x

Each cell in the grid is a radio button and the radio buttons in a row belong to one radio button group.

My models:

class Question
  # title
  has_many :answers
end

class Answer
  # name, position, atype(row/col)  
end

I am struggling to come up with a Rails approach for creating such a form. To complicate the issue user can save the semi-completed form and complete it at a later time.

What is the best approach for this problem?