[TYPO3-mvc] Working with input-fields but without saving to DB

[Stefan Frömken]

Hello,

I have to create a form to calculate the BMI and some other things.
I want to use the validator annotations to give feedback to the user if 
a field was not filled. But this annotations are made in the model-class 
and a model tries to store data in the db.

So how to tell my model to NOT store a field or a model to db?

Stefan