Wikipedia has categories that from what is perceived, should form a DAG (Direct Acyclic Graph). But very often they don't. I saw this with my own eyes when trie

Wikipedia has categories that from what is perceived, should form a DAG (Direct Acyclic Graph). But very often they don't. I saw this with my own eyes when tried to implement "DagView" (a visual control trying to navigate DAGs similar to trees). So you keep opening sub-categories and one of them suddenly is a super-category noticed before. This indicated for me that despite the fact that DAGs have luxury of having many "parents" it doesn't make things easy in the heads of those who try to work with them. Probably our brains are not very good at dealing with non-hierarchical structures