The HasChild ReferenceType is an abstract ReferenceType; only subtypes of it can be used. It is a subtype of HierarchicalReferences.
The semantic is to indicate that References of this type span a non-looping hierarchy.
Starting from Node “A” and only following References of the subtypes of the HasChild ReferenceType it shall never be possible to return to “A”. But it is allowed that following the References there may be more than one path leading to another Node “B”.