private Collection<UnitFileTag> materializeSelected(Unit unit) {
if (tags == null) {
String tagArray[] = selectedTags.split("\\p{Space}+");
this.tags = new HashSet<UnitFileTag>();
for (String element : tagArray) {
UnitFileTag tag = unit.getUnitFileTag(element);
if (tag != null) {
this.tags.add(tag);
}
}