But that’s his point: a hierarchy of tags embodies this “containment” metaphor rather than the flat approach traditionally implied by *tags*. There’s certainly value in a hierarchy, especially if it’s just a pseudo-hierarchy as hinted at by the tree-of-tags metaphore — but, at least to me, calling this structure “tagging” seems like a perversion of the concept. Perhaps, as Weinberger notes, “categories” would be more descriptive.