Monitoring minimum cost paths on road networks

On a road network, the minimum cost path (or min-cost path for short) from a source location to a destination is a path with the smallest travel cost among all possible paths. Despite that min-cost path queries on static networks have been well studied, the problem of monitoring min-cost paths on a road network in presence of updates is not fully explored. In this paper, we present PathMon, an efficient system for monitoring min-cost paths in dynamic road networks. PathMon addresses two important issues of the min-cost path monitoring problem, namely, (i) path invalidation that identifies min-cost paths returned to path queries affected by network changes, and (ii) path update that replaces invalid paths with new ones for those affected path queries. For (i), we introduce the notion of query scope, based on which a query scope index (QSI) is developed to identify affected path queries. For (ii), we devise a partial path computation algorithm (PPCA) to quickly recompute the updated paths. Through a comprehensive performance evaluation by simulation, QSI and PPCA are demonstrated to be effective on the path invalidation and path update issues.