Model without db backend for form validation?

As I gather, forms should be validated by a corresponding model. So here's my set up:

:subject has_many :calls

:call belongs_to :subject



I have a form that doesn't actually save, change, modify, etc any data. It just gathers a series of parameters so it can generate a report based on the subject and call models.

The subject and call models have their own set of validations that handle creation, updating, deletion etc.

The report won't be modifing any of these models, so I don't want them tied together.

What is the proper 'rails way' to do this?