  CSPTRQ is an interesting problem and its has attracted much attention. The
CSPTRQ is a variant of the traditional PTRQ. As objects moving in a
constrained-space are common, clearly, it can also find many applications. At
the first sight, our problem can be easily tackled by extending existing
methods used to answer the PTRQ. Unfortunately, those classical techniques are
not well suitable for our problem, due to a set of new challenges. We develop
targeted solutions and demonstrate the efficiency and effectiveness of the
proposed methods through extensive experiments.
