self.slot->select(sl : SlotType1 | (not sl.name.oclIsUndefined()) and sl.name='creationTime')->forAll(sl : SlotType1 | sl.valueList.oclIsUndefined() or 
	(sl.valueList.value->isEmpty()) or 
	( 
		(sl.valueList.value->size()=1) and 
		(sl.isDTM(sl.valueList.value->first())) 
	)    
)