Processing Directional Continuous Queries for Mobile Objects on Road Networks

Traditional location-based services for range queries or k nearest neighbor queries are omnidirectional, in which some query results are probably not interesting to a user because they are not on the way to destination. Due to the prevalence of guiding systems and the advances of electronic technologies and wireless communications, most mobile objects on roads move along with the pre- determined paths provided by path planning systems. With the concept of “by the way”, there would be an increasing demand on queries for objects on their paths and ahead of them. In this paper, we define the issues of directional continuous query for mobile objects on road networks. To address this issue, we not only propose the system architecture of a road network but also provide approaches to determine the safe period in order to efficiently update a directional query result. We elaborate cases of when to exclude a mobile object from a query result and when to insert a mobile object into a query result. Experimental results show that the network bandwidth dominates the preference of the adaptation of the centralized or distributed directional mobile query processing.