In OpenERP we can create many2one and one2many relationships between models very easily by creating many2one and one2many fields. You just need to declare a field in _columns and then using this field normally in the rest programming and views as we normally do.
I created a small module to explain called hospital, I have two objects patient and doctor. To establish relationship between these two entities or objects, create doctor_id field in patient model as many2one, and patient_id as one2many in doctor model.
The relationship can be explained as one doctor with many patients and many patients going to a single doctor.