Monitoring Spatial Keyword Queries Based on Resident Domains of Mobile Objects in IoT Environments

In IoT environments, geo-tagged data have rapidly been emerging as smart things, e.g., mobile devices or connected cars, are generally equipped with the global positioning system (GPS) module. A large volume of geo-tagged data can be fundamental to providing applications of location-based services (LBSs). One of the important LBS applications is to provide continuous spatial keyword queries. A continuous spatial keyword query monitors a designated region with a set of keywords. In the designated region, if mobile objects contain all the keywords of the query, they are the answer set for the query. The query continuously monitors the spatial region and reports its up-to-date query result. This paper presents a resident-domain-based approach for continuously monitoring spatial keyword queries. The proposed approach shifts the monitoring of tasks of affected queries from the server to mobile objects which have computational and storage abilities. According to their computational ability, the proposed approach assigns as large as possible resident domains to mobile objects. Within the resident domain, the mobile object informs the server about its spatial information only when crossing the boundary of its monitored queries, thereby reducing the communication cost between it and the server. The experimental evaluation has verified that the proposed approach outperforms the existing approach.