Multiple model validation

Hi

I'm doing multiple model validation. For example i've inquiry contact
and company models. My logic works in inquiries. So in inquiry model i
added validates_associated :contact, :company this. Now my doubt is when
i don't have any validation for inquires it is not accessing the company
and contact validation.

  To have these validation error messages do i have some validation in
inquiries?
How to do the multiple model validation?