对等数据管理系统中模式映射的备份机制

Backup Mechanism of Schema Mapping in Peer-to-peer Data Management System

针对对等数据管理系统中节点因自治性而动态离开和返回网络造成模式映射路径频繁断裂的问题,提出一种基于模式映射备份机制的离开节点绕过方法,向下游节点提供以树状结构组织的上游映射信息。当映射路径中有节点离开时,其下游节点的查询以此映射信息和备份的上游映射,绕过离开节点。仿真和分析的结果表明,映射备份机制的引入提高了查询的可达性,从而可以从更多的局部数据库中获得返回结果。

To address the problem of frequently broken mapping paths caused by peer dynamically departing and returning the network due to their autonomous nature in PDMS, an absent peer bypassing method is proposed based on schema mapping backup mechanism, which provides tree-structure organized mapping information to the downstream peers. When a peer departs in the mapping path, queries of its downstream peers rely on the mapping information and the backup upstream mappings to bypass the absent peer. Simulation and analysis result shows that the in mapping backup mechanism increases the query achievability, so that results can be returned from more local databases.