Boundedness of Regular Path Queries in Data Integration Systems

In this paper, the authors study the problem of deciding whether a regular path query over views in data-integration systems can be re-expressed without recursion. The problem becomes challenging when the views contain recursion, thereby potentially making recursion in the query unnecessary. They define two related notions of boundedness of regular path queries. For one of the notions they show it PSPACE complete, and obtain a constructive method for optimizing regular path queries in data-integration systems. For the other notion of boundedness, they show it PTIME reducible to the notorius problem of limitedness in distance automata, for which only exponential time algorithms are currently known.