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
基于组通信系统的数据库复制将一些单个的数据库组织成一个逻辑数据库,可以提高其可用性和产量并支持更多用户。中间层数据复制用一种中间层的C/S模式来截取客户端和数据库交互的数据流,将用户请求送到所有节点执行。组通信系统和2PC被...基于组通信系统的数据库复制将一些单个的数据库组织成一个逻辑数据库,可以提高其可用性和产量并支持更多用户。中间层数据复制用一种中间层的C/S模式来截取客户端和数据库交互的数据流,将用户请求送到所有节点执行。组通信系统和2PC被用来保证复制数据库严格的一致性。本文提出了一种面向操作的复制协议和一种面向事务的记录一重放协议。基于组通信系统的发展和国产的DBMS of Kingbase模式,面向操作的复制服务得到了实现。本文的工作表明利用组通信可以在中间层实现透明复制并可以取得较好的性能。展开更多
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.
文摘基于组通信系统的数据库复制将一些单个的数据库组织成一个逻辑数据库,可以提高其可用性和产量并支持更多用户。中间层数据复制用一种中间层的C/S模式来截取客户端和数据库交互的数据流,将用户请求送到所有节点执行。组通信系统和2PC被用来保证复制数据库严格的一致性。本文提出了一种面向操作的复制协议和一种面向事务的记录一重放协议。基于组通信系统的发展和国产的DBMS of Kingbase模式,面向操作的复制服务得到了实现。本文的工作表明利用组通信可以在中间层实现透明复制并可以取得较好的性能。
