Is it possible to make the second selection required for validation only if the 'yes' option is selected in the first one?
<div class="form-group" ng-class="{ 'has-error' : articleEditForm.pnp.$invalid && !articleEditForm.pnp.$pristine }">
<label class="control-label col-sm-2">Working? (yes/no) *</label>
<div class="col-sm-10">
<select class="form-control" name='pnp' id='pnp' ng-model="article.pnp" ng-options="o.value as o.option for o in items" required></select>
</div>
</div>
<div class="form-group" ng-class="{ 'has-error' : articleAddForm.idpnpgrupe.$invalid && !articleAddForm.idpnpgrupe.$pristine }">
<label class="control-label col-sm-2">Pnp group </label>
<div class="col-sm-10">
<select class="form-control" name='idpnpgrupe' id='idpnpgrupe' ng-model="article.idpnpgrupe" ng-options="o.id as o.opis for o in catchpnpgrupe"></select>
</div>
</div>