Intranets are more coherent than the Internet because they are more focused. General libraries are not coherent collections because they cover the gamut. A library filing system is simply a coherent approach to an incoherent collection, but it can be used within postcoordinate thematics. For an example of how to use the Dewey Decimal system. Categories are never objective, and never sufficiently detailed for our interests, goals, or resources.
Categories are relics of print technology and historical academic conventions.
They are limiting habits that now largely obscure the focused access we are trying to achieve. Fuzziness is an essential but still neglected aspect of retrieval languages. For more on fuzzy attributes and their uses. Categories are simplistic but full text search is also simplistic, because word definitions depend on context. Words have infinite contexts.