A specific example would be helpful. Keep in mind that some many-to-many relationships will not conform to hierarchical referential integrity rules. In DRM those cases will have to be handled with attribution.
Many to many relationships can be facilitated with a 'global' node and it's local members, which may be the same node, but have a different prefix based on it's downstream requirements. Each of the 'sub' nodes can be related to the same node as it's parent (associated node).
If there are no real shared ancestors, then alternate hierarchies are built. Since the same node (named the same) is 'linked' in each hierarchy, it will carry the same global property relationships as the first instance of the node.