一种移动数据库管理系统的体系结构

移动计算的网络环境具有其鲜明的特点：移动性、断接性、带宽多样性、可伸缩性、弱可靠性、网络通信的非对称性、电源能力局限笥等等。而现有的DBMS不能很好地解决移动计算环境中的数据库管理问题，因此有必要设计适于移动计算的数据库管理系统，首先分析了移动计算环境数据库系统的本质，指出移动数据库是一种动态分布式数据库。由于运动是相对的，即客户机被假定静止时，则服务器是动态变化的，通过引入虚拟服务器的概念可以将客户机的“移动”转换为服务器的“移动”，在此基础上，提出了一种移动数据库管理系统的体系结构，这种结构具有一定的通用性，该结构由虚拟服务器和局部DBMS组成，其中虚拟服务器是核心，对它的功能进行了详细的讨论，最后还介绍了基于此体系 结构和自主开发的分布式数据库管理系统DM2上的一个移动DBMS原型。

AN ARCHITECTURE OF MOBILE DATABASE MANAGEMENT SYSTEM

The network environment of mobile computing has bright characteristics: mobility, disconnection, bandwidth diversity, scalability, weak reliability, non symmetry of network communication, limits of power ability, etc. Existing DBMS can't manage database efficiently in mobile computing environment, so it is necessary to design a new kind of DBMS which is suitable for mobile computing. In this paper, the essence of database system in mobile computing is analyzed and it is concluded that the mobile database is a kind of dynamical distributed database. Because of the relativity of mobility, it can be seen that if the client is considered to be static, then the server is dynamical. So the concept of virtual server to translate the clients' mobility to servers' mobility is introduced in this paper. Based on these opinions, a kind of architecture of mobile DBMS is proposed, which is of versatility. The architecture is composed of virtual server and local DBMS. The function of virtual server is the kernel of the architecture and described in details. Finally, a mobile DBMS prototype is introduced based on the DM2 developed.