helper context Entity def: entities(): Sequence(Entity) = self;
helper context Group def: entities(): Sequence(Entity) = self.elements->collect(e|e.entities())->flatten();

helper def: fields: Sequence(FileDefinition!FieldDefinition) =
	Sequence{};

helper context GradingSystem!TaskGroup def : getConcreteTasks() : Sequence(FileDefinition!FieldDefinition ) =
	self.contains->iterate( child ; elements : Sequence(FileDefinition!FieldDefinition ) = 
		Sequence{} |  
		if child.oclIsTypeOf(GradingSystem!TaskGroup) then			
		(
			( elements.union(child.getConcreteTasks()))			
		)-- TaskGroup : recursive call			
		else
		(		  
			thisModule.fields.union((elements.append(thisModule.NewStaticField(self.name+child.name+'Points', 'Integer'))) )
			-- cant store the actual elements sequence in the helper fields, thisModule.field always stays empty
any other possibilities to store this? 


		)  -- ConcreteTask
		endif  
		) -> append(thisModule.NewAgreggField(self.name,'Integer',thisModule.fields )) -- here i would need the thisModule.fields
		
	;