bindings: {

                    itemType: '<?',

                }

someController = function someController( $scope) {
            var self = this;

            self.itemType = 'someString';

<some-component>
        open-id="singleSelect"
        item-type="ctrl.itemType"

itemType.currentValue = 'someString'

<some-component>
        open-id="singleSelect""
        item-type="someString"

itemType.currentValue = undefined