This an issue of growing ontologies and taxonomies. I have found that the best answer I have is: 1) Gossip and use the existing ontology and add new items onl

This an issue of growing ontologies and taxonomies. I have found that the best answer I have is: 1) Gossip and use the existing ontology and add new items only if genuinely needed 2) Combine synonyms, sometimes using vector embedding and cosine similarity during search The insight is that trees are not a storage constraint but a traversal consequence — any walk through a graph starting from a given node produces a tree as a byproduct, and different starting points or orderings produce different trees from the same underlying structure. Rather than forcing a choice of canonical hierarchy at write time (the dentist-bill-goes-in-which-folder problem), you store the graph and let the tree emerge lazily from context: whoever is querying, from wherever they enter, gets the tree that is relevant to them, and no connections are sacrificed to produce it. In general, federated systems have this quality emerge. For example, in OpenStreetMap, one group can label Nagorno Karabakh, the other Artsakh, and no one has to fight Google etc.