Model without db backend for form validation?

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

has_many :calls

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?