<div>
    <label class="radio">
        <input type="radio" name="orderDirection" value="asc" ng-model="model.value" />
        Ascending <code>[a-z]</code>
    </label>
    <label class="radio">
        <input type="radio" name="orderDirection" value="desc" ng-model="model.value" />
        Descending <code>[z-a]</code>
    </label>
    
    <span class="help-inline" val-msg-for="orderDirection" val-toggle-msg="required">Required</span>
</div>