r:graphValidator is a component which allows to perform Object validation. value attribute should be defined with the value binding to bean. In the result all the bean properties will be validated during validation phase. That allows you to validate all the object properties and not just ones which are submitted with the current request.

Simple but probably most common example of such kind of usage is shown below. Below is the simple sample of cross-field validation. Passwords getting validated according to constraints for every field and isPasswordEquals validation check if them are equals.