Bounded regular path queries in view-based data integration

In this paper we study the problem of deciding boundedness of (recursive) regular path queries over views in data integration systems, that is, whether a query can be re-expressed without recursion. This problem becomes challenging when the views contain recursion, thereby potentially making recursion in the query unnecessary. We define and solve two related problems of boundedness of regular path queries. One of the problems asks for the existence of a bound, and the other, more restricted one, asks if the query is bounded within a given parameter. For the more restricted version we show it PSPACE complete, and obtain a constructive method for optimizing the queries. For the existential version of boundedness, we show it PTIME reducible to the notorious problem of limitedness in distance automata. This problem has received a lot attention in the formal language community, but only exponential time algorithms are currently known.