Vsystem Architecture

Vsystem Architecture:
Modular, Flexible, Scalable

Most operating systems support:

Independent processes that can be initiated and deleted independently.
Shared global sections.
Interprocess event delivery.

Vista Control System's Vsystem architecture exploits these features in its modular, flexible, and scalable architecture.

How can one picture this architecture? Consider an electronic bus, such as a VME, PLC, or computer backplane, into which functional modules are plugged to make up the overall system. Our real-time database, Vaccess, can be thought of as the backplane, and the other products, and user-written application code, are the modules that are plugged in--in fact they are hot-swappable as a result of the independent process feature of the operating system and the internal design and implementation of Vaccess. While electronic busses transmit data from a master to one (or more) slaves and interrupts from slaves to masters, Vaccess can do more. Implemented as a shared global section with an API, Vaccess more closely models the data structures and requirements of real-time monitoring and control systems.

The channels of Vaccess are the items of data that reflect the information associated with the application. What that really means is that for each input sensor, temperature, pressure, status, flow, and so forth, there is an input channel defined with the appropriate name. And for every control, open/close command, pump speed, on/off command, and so forth, there is an output channel in Vaccess.

You can add channels to Vaccess that are used for high-level commands, derived data, and intermediate data. You can then fully exploit the power of the Vaccess architecture by breaking down complex applications into the logical components and implementing and testing them separately as computer processes communicating through Vaccess.

Each channel has many fields that can be used to centralize the information about that channel and add features to the processing of the gets and puts of values. These features include

Data conversion
Alarm checking
Output clipping
User-defined value processing
Data formatting

Other important aspects of Vsystem are its scalability and networking. Because of the overhead of the TCP/IP stack and the limited bandwidth of the network connection, Vsystem is designed to use the overall system as efficiently as possible. To achieve this, any process on the network can not only read the current value of a channel and any field of any channel, but it can also request notification of change of that field or any other field. Thus:

Only data that have been requested and have changed are transmitted.
Change events to be transmitted over the network are combined into messages.

Benefits of the Vsystem Architecture

You are not required to shut down the whole system to make a single change--only the component affected need be shut down and restarted.
If a component fails for any reason, the rest of the system will keep running and the failed component can be restarted.
Functionality is isolated in modules, making development and testing more predictable and reliable.
Because data are shared on a common bus, any process has access and can thus display them, process them, and archive them to disk.
Because the API is network-independent, processes can be moved between computers without changes.
Vaccess database channels can be defined for internal data and commands, such as “efficiency” and “stop process.”
Replacing the I/O connection module with a process simulator results in a training system.
Removing the I/O connection module and using Playback allows the system to be used to study previously recorded operations.

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Updated Mar 31, 2006