\ontology#test
	\struct#test[root=true]
		\field
			\childRef[a]
			\childRef[b]
			\childRef[c]
	\struct#b
		\primitive[type=@a]
	\struct#c
		\field
			\childRef[a]
			\childRef[b]
			\childRef[c]
	\struct#a
	\struct#d[isa=a]