New Control System Aspects for Supporting Complex Data and High Performance System

items, structured items, strings, integers, sequences of bytes, XML data, OPC binary and so forth. Each data item is accompanied by a Data Type Description that defines the structure of the item and a Dictionary described each of the Data Types. The dictionary contains all information that the OPC client needs to be recognized the complex data item it is receiving. The OPC complex data specification defined two type systems that provide the level of capability, XML schema and OPC binary. The XML schema describes complex data values that are presented in XML. The OPC binary which is used to present complex binary values has defined the format of OPC binary dictionaries. 2.3 Problem Statements The data in the industrial systems can be normally acquired not only from different field systems and devices, but also from different OPC servers. Currently, OPC clients can only read and decode the data as a simple data type. However, the data 398 Dae-Seung Yoo et al. Journal of Computing Science and Engineering, Vol. 2, No. 4, December 2008 from the hardware I/O devices are complex data such as pressure, temperature, flow, level, and vibration or discrete signals, and so forth [Tan et al. 2006; TheOPCFoundation 2003; Iwanitz and Lange 2006]. In addition to the automation and control systems the OPC clients can read, write, and subscribe to thousands of data points from various I/O devices through the OPC servers. For a graphical presentation of the large data mounts of the process data on the OPC clients, a large data transfer from the OPC server to the OPC clients may consume a large amount of the network bandwidth and operating system resources. Due to these requirements, the additional improvements for large network control systems using the OPC DA standard are required to reach an acceptable performance. There are a number of researches focused on COM technology 2