Ontology/taxonomy/classification are seriously difficult things. If not semantic web would have ruled the world by now. Structural hierarchies (chapter/section

Ontology/taxonomy/classification are seriously difficult things. If not semantic web would have ruled the world by now. Structural hierarchies (chapter/section etc) may be easy to get for everyone but a navigation side panel would work too. If you build a semantic hierarchy, new users may not know how to find things; yet repeat users may be frustrated by having to go through the layers to access the items they are looking for.