code: public Rules add(PropertyConstraint constraint) {
  		CompoundPropertyConstraint and = (CompoundPropertyConstraint)propertiesConstraints.get(constraint
  				.getPropertyName());
  		if (and == null) {
  			putPropertyConstraint(constraint);
  		}
  		else {
  			and.add(constraint);
  		}
  		return this;
  	}
docs: Adds the provided bean property expression (constraint) to the list of
  constraints for the constrained property.
  
  @param constraint
  the bean property expression
  @return this, to support chaining.