Proper place for validating records on save and warn user?

[htgoebel (Hartmut Goebel)]

I need to validate records on save and issue a UserWarning in case the record is not valid.

Which is the proper place for this validation? pre_validate(). validate() or somewhere else?

[pokoli (Sergi Almacellas Abellana)]

validate is the right method to do such validations.