Opc data Access Automation Specification

1.2

 

Purpose 

What is needed is a common way for automation applications to access data from any data source like a device or a 

database. 

The OPC Data Access Automation defines a standard by which automation applications can access process data.  This 

interface provides the same functionality as the custom interface, but in an “automation friendly” manner. 

Given the common use of Automation to access other software environments (e.g.: RDBMS, MS Office applications, 

WWW objects), this interface has been tailored to ease application development, without sacrificing functionality 

defined by the Custom interface. 

The figure below shows an Automation client calling into an OPC Data Access Server using a 'wrapper' DLL. This 

wrapper translates between the custom interface provided by the server and the automation interface desired by the 

client.  Note that in general the connection between the Automation Client and the Automation Server will be 'In Process' 

while the connection between the Automation Server and the Custom Server may be either In Process, Local or Remote.  

 

10 

 

Automation Client

OPC Automation Wrapper

OPC Custom Interface Server

COM / DCOM

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 1-1.  Custom and Automation Client Applications Interfacing to OPC Servers 

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OPC Data Access Automation Specification2.02