Design of Web Service by Using OPC XML-DA and OPC Complex Data for Automation and Control Systems

Web technologies are gaining increased importance in automation and control systems. However, the choice of Web technologies depends on the use cases in the application environment. In industrial systems, the data can be got not only from many different field systems and devices but also from different OPC (OLE for Process Control) Servers. Current OPC Client might be able to read simple data from OPC Server, but there are some problems to get structured data and to exchange structured information between collaborating applications. Therefore, OPC Foundation has defined interfaces to OPC XML-DA (OPC XML Data Access) and OPC Complex Data that aim to solve those problems. The OPC XML-DA can facilitate the exchange of plant data across the internet, and upwards into the enterprise domain. In addition, the OPC Complex Data will extend the OPC DA specification to allow the OPC Client to read and decode any type of data from measurement and control systems on the plant floor. This paper will describe the concept of OPC XML-DA and OPC Complex Data. And then it proposes a mechanism to implement the OPC Complex Data into OPC XML-DA Server. Additionally, the paper also discusses the security aspects.