16. A device as claimed in claim 13 , wherein the path-decomposed trie is a binary tree and is hollow in that the labels comprise only a skip sequence interleaved with directions taken in a centroid path, and a first one of the plurality of arrays stores the labels of the path-decomposed trie by interleaving the labels with the directions.
16. A device as claimed in claim 13 , wherein the path-decomposed trie is a binary tree and is hollow in that the labels comprise only a skip sequence interleaved with directions taken in a centroid path, and a first one of the plurality of arrays stores the labels of the path-decomposed trie by interleaving the labels with the directions. 17. A device as claimed in claim 16 , wherein the first one of the plurality of arrays comprises two aligned bit vectors to represent the labels, in a first of the two aligned bit vectors the skips are incremented by one and binary representations of the skips are interleaved with the directions and concatenated.