Compact representation for answer sets of [formula omitted]-ary regular queries

Abstract

An n -ary query over trees takes an input tree t and returns a set of n -tuples of the nodes of t . In this paper, a compact data structure is introduced for representing the answer sets of n -ary queries defined by tree automata. Despite that the number of the elements of the answer set can be as large as | t | n , our representation allows storing the set using only O ( | t | ) space. Several basic operations on the sets are shown to be efficiently executable on the representation.