Boundedness of Regular Path Queries in Data Integration Systems

In this paper we 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 unecessary. We define two related notions of boundedness of regular path queries. For one of the notions we show it PSPACE complete, and obtain a constructive method for optimizing regular path queries in data-integration systems. For the other notion of boundedness, we show it PTIME reducible to the notorious problem of limitedness in distance automata, for which only exponential time algorithms are currently known.