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Section 6, the component-oriented architecture is
implemented into distributed production system. And
Section 7 gives a conclusion of the work.
2. BASIC OBJECTS OF A SCADA SOFTWARE
From reading and analyzing [5-7], a common picture
of objects in a SCADA software and their interaction is
shown in Fig. 1. Basic SCADA software has four main objects: I/O
driver, data center, designer, runtime and four other sub
objects: trend, alarm, report and network connector.
I/O driver gets real-time data from devices to give to
other objects in software. The real-time data is
represented by values of tags in SCADA software.
Data center stores raw values or processed values of
specified tags into database. Data center has four other
sub objects: trend, alarm, report and network connector.
Trend or, more exactly, real-time trend uses data
directly from I/O driver object or stored data in database
to draw charts.
Alarm object uses real-time data from I/O driver
object to announce exceeding statuses of values to users
and these statuses are also stored into database.
Report object uses stored data of database to print
report papers or display onto screens numerically.
Utilities of trend, alarm and report objects are
configured and viewed in designer and runtime by trend-
viewer, alarm-viewer, report-viewer respectively.
Network connector object allows accesses from
outside of SCADA station or from other third-party
applications to the database to collect data or to use
resource of data center.
Designer is a user interface. It includes many design
tools, such as labels, textboxes, alarm-viewer, report-
viewer, trend-viewer, etc. to display values of tags;
buttons, switches, etc. to change values of tags. It can
specify whichever tags will log their values into database
or be used in trend, alarm or report objects. Designer is
used by system engineers to design plant picture to
monitor and control processes in plant. After designing
in designer, system engineers have to save their work
into a project file. This file will be read and executed by
runtime object.
Runtime is an executive object of the project file
created by designer. It is used by operators to monitor
and control processes in plant.
Functions of designer and runtime are shown in Fig. 2.
In the package GeniDAQ (Advantech, Taiwan), GeniDAQ Builder and GeniDAQ Runtime are designer
and runtime respectively. In the Intouch (Wonderware,
USA), Window Maker is designer and Window Viewer
is runtime.
After applying some SCADA software packages, such
as WinCC (Siemens, Germany), Intouch, GeniDAQ into
many plant projects, we realized that they included
nearly all of new technologies, but they are cumbersome,
because they are based on modular programming [5-7]
which is an old programming technique. They are
developed from their first version which is analyzed and
designed upon old technologies and many update patches.
So, they are larger and larger, they become complex
systems. A software package is installed in only one
computer, so all of its resources are in that computer. If a
plant wants to apply client-server topology for SCADA,
many same SCADA software packages have to be
bought to install in the computers, but they only use
resources on servers, not all of resources on clients are
used.
3. COMPONENT-ORIENTED PROGRAMMING
Component-oriented programming (COP) is a modern
programming technique which enables programs to be
constructed from software components. A software com-
ponent is a piece of self-contained, self-deployable com-
puter code with well-defined functionality and can be