A full and linear index of a tree for tree patterns

Abstract

A new and simple method of indexing a tree for tree patterns is presented. A tree pattern is a tree whose leaves can be labelled by a special symbol S, which serves as a placeholder for any subtree. Given a subject tree T with n nodes, the tree is preprocessed and an index, which consists of a standard string compact suffix automaton and a subtree jump table, is constructed. The number of distinct tree patterns which match the tree is O(2n), and the size of the index is O(n). The searching phase uses the index, reads an input tree pattern P of size m and computes the list of positions of all occurrences of the pattern P in the tree T. For an input tree pattern P in linear prefix notation pref(P)=P1 SP2S...SPk, k ≥ 1, the searching is performed in time O(m + Σi=1k|occ(Pi)|)), where occ(Pi) is the set of all occurrences of Pi in pref(T). © 2014 Springer International Publishing.