“In a formal taxonomy, a single root node sits atop the hierarchy. Properties flow from class to subclass through the principle of inheritance. Each object and category is assigned a single location within the taxonomy. We live at an address within a nested hierarchy of streets, cities, states, and countries. We exist as Homo Sapiens within the taxa of domain, kingdom, phylum, subphylum, class, order, family, genus, and species.
Of course, the world doesn’t always cooperate with this Platonic approach cation. Fish with lungs. Mammals that lay eggs. Documents about tiple topics. Words with many meanings. Meanings with many words. Reality confounds mutually exclusive classifications, and so we find ourselves debating which exlsting category works best or defining new categories to allow a perfect fit. Lumpers and Splitters have been haggling over the Linnaean taxonomy of living things for the past few centuries.”
From: Morville, Peter (2005), Ambient Findability, Sebastopol: O’Reilly, p.127