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When accessing an object by reference (or marshaling
by reference), client uses a proxy as a reference to the
object in sever computer. A proxy in client side is an
object that provides exactly the same interfaces, public
methods, properties, and members as the real object in
the server side, but it is not a copy of the real object, it is
just a material for client to make a reference to server
side object. With this option of accessing, client can
write value to the server side. This is suitable for remot-
ing SCADA application. Moreover, the kind server-
activated-single-call of marshaling by reference can be
applied for saving resource of server computer.
With the component framework, search mechanism,
remoting technology and the good support of .NET for
component and remoting, this pattern can fully manage
all interactions of components without depending on the
distance of components in physical network. This can
help us to distribute components into computer network
to make a distributed SCADA system. Thus, we can take
advantage of many processors to increase processing
speed.
Applying basic objects of a SCADA system into the
design pattern described in Fig. 4 on .NET platform, a
component-oriented architecture for SCADA system is
proposed (Fig. 6). It inherits all good characteristics of
software component and the design pattern.
In Fig. 6, designer module and runtime module are
clients they have their own component framework,
which help them find their servers. Graphic library com-
ponent is a server providing indicators and control ob-
jects for plant picture in designer and runtime. Trend,
alarm and report components also are servers, they pro-
vide their specific services (described in Section 2) for
designer and runtime. I/O driver server connects to phys-
ical devices to acquire real-time data and provides real-
time data for its clients (designer, runtime, trend, alarm,
report) in the form of values of tags. Database compo-
nent is used by trend, alarm, and report for archiving tag
values.
Designer module and its component framework are
packaged into a package. Runtime module and its com-
ponent framework are also in the same package. These
packages are installed in computers and these computers
are clients. The server components can be installed sepa-
rately in many computers. They can execute indepen-
dently in their computers to provide their necessary ser-
vices to clients.摘要：适合分布式控制系统的数据采集与监视控制软件是系统开发必要的需求因为现有的数据采集与监视控制系统软件的特点难以满足分布式系统的需求。对于面向构件技术的优势，本文提出了一个面向组件的结构的数据采集与监视控制系统软件去满足分布式控制系统的需求。设计模式和OPC（过程控制的对象连接与嵌入）技术也用于制造开放的体系结构。
关键词：面向组件的编程；分布式控制系统；实时设计模式；实时系统；数据采集与监视控制；系统结构
1. 介绍
数据采集与监视控制系统被称为监视收集来自物理设备的数据的过程的软件，在电脑上存档和应用计算机控制的设备的命令。数据采集与监视控制系统包括主要建立在计算机基础设施的基础上的一些过程（可能是一台电脑或者一个计算机网络）和安装在电脑上的数据采集与监视控制软件。
通过大规模的生产需求，生产率，质量和安全，目前的生产系统是大的和复杂的。这些系统的移动设备被安装在范围宽广的工厂里并且它们的状态由多个部门所监视和控制。这些被称为分布式控制系统。在本文讨论的电力系统是一个例子。它们需要高级的数据采集与监视控制软件而且有如下几个特点：独立的距离，灵活的操作，简单的升级，合理的监控成本和在广泛的领域中控制所有的分布式设备。