Dependent Filelds dependencies

Can any one tell me where the dependency of the dependent fields is maintained . is it saved in database if yes then in which table ?? or there is another method it uses to maintain dependencies.
here by dependencies i mean that which field is controlled by which field and which data have to display.
example-> i have created fields Country, State, City state depending on country and city on state field and i also filter their values by there controlled fields so i want to know where this relationship status is stored