The Implement Of Data Access Service Based On Middleware

In the distributed control system, each subsystem has different communication system and protocol, and there is lack of common communication interface among them. So it's difficult to access and manage data between the subsystems and the management system. Data access middleware provides a better solution to improve the openness of the distributed control system.Based on the discussion of middleware, this thesis studies current OPC series specification, and suggested that a middleware layer should be added on current criterions so as to establish a real opening middleware criterion for industrial control systems. According to the characteristics of industrial control systems and the requirements analysis of data access middleware, a three-layer C/M/S architecture is proposed and its corresponding system model is also developed. The solution takes the advantage of object-oriented modeling technology. We design and implement a data access middleware, which promises the user access data transparently.