|
PS/SL Middleware Project Remote Device Access API |
||||||||
| PREV NEXT | FRAMES NO FRAMES | ||||||||
See:
Description
| Packages | |
| cmw.rda | Contains common classes which are used by both client and server packages. |
| cmw.rda.client | Provides classes and interfaces which client applications need in order to communicate with remote Devices. |
| cmw.rda.server | Provides base classes for implementing various device servers. |
| cmw.rda.server.test | Provides a simple device server implementation used for the RDA test. |
This document is the API specification of the Remote Device Access (RDA) subsystem.
The RDA subsystem provides facilities that clients (end-user applications or middle-tier servers) use to communicate with accelerator devices conforming to the standard Device/Property model. The model defines a device as a named entity in the control system that has properties. Each property has a name and a value. The value can be of a simple data type or a complex record with a number of named fields, or characteristics. The values can be read, written or monitored by clients using the basic access methods defined in the standard device interface (get, set, monitorOn/Off). The devices are organized in classes; all devices belonging to the same class share the same set of the property definitions (names, semantics and value types).
Physically, devices are implemented in Device Servers which typically reside in the front-end computers (DSC) but, in principle, can run anywhere in the control network. The main purpose of the RDA subsystem is to provide for the clients location transparent and reliable access to the devices. This includes remote invocation of the device access methods in all model-defined modes (synchronous, asynchronous, subscription) and transparent delivery of the invocation results (property values or exceptions) back to the clients.
The RDA also provides a minimum framework for Device Servers implementation: a set of software components required to make a Device Server "RDA-enabled". The actual server implementation, however, is outside of the RDA scope. For this reason, the RDA API specifies the expected rather then "exact" behavior of the device access methods and sometimes gives rather broad definitions of method parameters and results. You may need to consult the corresponding Device Server and/or device class documentation in order to clarify semantics of the methods and exact meaning of parameters.
|
Version 1.0 August 2000 N.Trofimov |
||||||||
| PREV NEXT | FRAMES NO FRAMES | ||||||||