A new update strategy, distance-based update strategy, is presented in Location Dependent Continuous Query (LDCQ) under error limitation. There are different possibilities to intersect when the distances between movin...A new update strategy, distance-based update strategy, is presented in Location Dependent Continuous Query (LDCQ) under error limitation. There are different possibilities to intersect when the distances between moving objects and the querying boundary are different.Therefore, moving objects have different influences to the query result. We set different deviation limits for different moving objects according to distances. A great number of unnecessary updates are reduced and the payload of the system is relieved.展开更多
With the advances in mobile computing and mobile communication technology, there comes a kind of novel applications in which the locations of moving objects are maintained and processed. In existing literatures, a dat...With the advances in mobile computing and mobile communication technology, there comes a kind of novel applications in which the locations of moving objects are maintained and processed. In existing literatures, a data model called moving objects sptio-temporal (MOST) is proposed and a new location record is generated when the distance between the actual location and the database location of a moving object exceeds a pre-defined distance threshold. In a mobile computing environment, a user can issue location-dependent continuous queries (LDCQs). To cater for the large number of moving objects in the system, this paper first gives a hierarchical distributed location database model to store the locations of moving objects. Based on the distribution of the location databases for different moving objects, this paper then proposes a method to determine the processing site for a location-dependent query. When a LDCQ is processed, a set of tuples <O, begin, end> Is provided indicating that object O satisfies the condition presented in the LDCQ from time begin to end. In the existing literatures, when there is a location update generation, the related LDCQ is re-processed and the answering tuples are re-transmitted via the wireless channel. This location-update-based LDCQ processing method has its disadvantages: it has much CPU calculation cost and imposes a high overhead in the wireless bandwidth which is very undesirable In a wirelss environment. Based on the maximal speed of a moving object, this paper presents a deferred LDCQ evaluation strategy.展开更多
文摘A new update strategy, distance-based update strategy, is presented in Location Dependent Continuous Query (LDCQ) under error limitation. There are different possibilities to intersect when the distances between moving objects and the querying boundary are different.Therefore, moving objects have different influences to the query result. We set different deviation limits for different moving objects according to distances. A great number of unnecessary updates are reduced and the payload of the system is relieved.
文摘With the advances in mobile computing and mobile communication technology, there comes a kind of novel applications in which the locations of moving objects are maintained and processed. In existing literatures, a data model called moving objects sptio-temporal (MOST) is proposed and a new location record is generated when the distance between the actual location and the database location of a moving object exceeds a pre-defined distance threshold. In a mobile computing environment, a user can issue location-dependent continuous queries (LDCQs). To cater for the large number of moving objects in the system, this paper first gives a hierarchical distributed location database model to store the locations of moving objects. Based on the distribution of the location databases for different moving objects, this paper then proposes a method to determine the processing site for a location-dependent query. When a LDCQ is processed, a set of tuples <O, begin, end> Is provided indicating that object O satisfies the condition presented in the LDCQ from time begin to end. In the existing literatures, when there is a location update generation, the related LDCQ is re-processed and the answering tuples are re-transmitted via the wireless channel. This location-update-based LDCQ processing method has its disadvantages: it has much CPU calculation cost and imposes a high overhead in the wireless bandwidth which is very undesirable In a wirelss environment. Based on the maximal speed of a moving object, this paper presents a deferred LDCQ evaluation strategy.
