ActiveX
Controls
Food Processor Analogy
What is an ActiveX Control?
An ActiveX control
in Windows 95/98/98 is like a grating wheel is for a food processor.
The good old food processors provided a motor, a connection point
to the motor, a collection bucket and a input feeding device -Then
the user had to select the best slicing, dicing, pureeing attachment
in order to process the food correctly.
In this analogy, Windows 95/98/NT
provides the motor (the operating system itself), the connection
point (support for ActiveX Controls), a collection bucket (the different
applications that can utilize ActiveX components), and an input
feeding device (access to computer I/O such as serial ports and
the Internet). So, now we plug in our favorite cutting edge attachment
(the ActiveX control). This ActiveX Control defines what type of
inputs to process (you may want data from a device) and what to
do with the input - such as display the data or store the data.
From a technical/functional view,
ActiveX controls are simply another Windows program with the ability
to receive and process inputs, to generate outputs and display information,
to be loaded when needed and expelled when its task is complete,
to generally perform a useful operation upon request. The only marked
difference is that the operating system doesn't directly execute
an ActiveX Control for measuring temperature, but the operating
system does call a Windows 95/98 executable more or less directly
(i.e., when user sees MS Word icon and selects that icon in order
to start doing some Word Processing). In the hierarchy of the computer,
the Operating System is host to the Executable Application, and
the Executable Application is host to the ActiveX Control.
If a manufacturer is providing
configuration software for a device, that software can be created
as an Executable Application to be started from a Windows Icon or
the software can be created as an ActiveX Control to be accessed
as part of a web page on the user's computer. The difference here
is trivial.
The real power comes by automatically
feeding readings from one ActiveX Control (which is obtaining temperature
measurements), with another ActiveX Control that is monitoring power
inputs to a system, and then obtaining historical trending to help
a Plant Manager determine when heating efficiency is optimal or
discover when maintenance is required.
More Power To The Industry.
Currently the Process Control industry
focuses on providing Object Linking and Embedding for Process
Control (OPC) software. Object Linking and Embedding (OLE)
is the predecessor to ActiveX and both use the same technology.
Essentially, within the scope of this discussion, OLE and ActiveX
are practically the same.
(The OPC driver is an
ActiveX that specializes in retrieving reading data and alarm status
from process control and monitoring devices. Under OPC, data acquisition
software locates devices based on an industry standard identification
method, namely that of associating devices with groups, items and
tags.)
OPC makes for easiest connection
of drivers into major Process Control industry applications. OPC
was developed for the Industry and hence has the simplest integration
into Industry-related products. But the task of utilizing OPC servers/drivers
(i.e. Software to extract data from Process Control devices and
share the data in OPC format to programs that requested or ordered
the data - the clients) with non-OPC products isn't easy or trivial.
ActiveX technology offers a means
of retrieving data from Process Control devices which is compatible
with many Process Control applications as well as with standard
Windows applications. For Process Control and Data Acquisition programs,
ActiveX isn't as conventional (as OPC), yet depending on the application
use of ActiveX controls can still be trivial. If instead, you seek
to access devices from within Visual Basic (version 5 or newer)
or via Excel (Excel 97 or newer), or Internet Explorer (ver 4.0
or newer), data access can be as simple as merely inserting the
ActiveX Control into the application and watching the ActiveX display
the readings - that's how easy an ActiveX obtain results.
Simplicity may be found even
for more complex applications. ActiveX controls may obtain data
from devices through a programming feature that has an easily identifiable
name such as MainReading.
Final Thoughts (or Food
for Thought)
Development of the iSeries ActiveX
focused on using the cutting edge technology under Microsoft Windows
so that users and programmers at all levels of experience would
be able to access data from Newport devices. By providing an ActiveX
control, we give customers a specialized attachment to the Microsoft
food processor. Then, when a customer wants to get temperature or
process values from the iSeries devices, he simply inserts the iSeries
ActiveX ( or attachment) into the collection bucket and hits the
Start button.
Hence we want to extend
the power of tools that people currently have. If they have Windows
(with the Internet Explorer), they can display iSeries readings
in a Web page (and could log readings if so inclined). If they are
familiar with Excel, then they combine the power of the iSeries
ActiveX with the data manipulation power of Excel. Or if they want,
they can insert our ActiveX into Rockwell Automation projects. The
Windows user doesn't have to buy other software, but may get other
software if desired.
As seen from the similarity to
food processors, the strength of the iSeries ActiveX lies in the
offering of power, flexibility, economy, and simplicity to the end-user.
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