This specification is intended as reference material for developers of OPC Automation Clients that require the
functionality of the OPC Historical Data Access Custom Interface.
The developer needs some knowledge of basic Automation concepts and terminology.
The fundamental design goal is that this interface is intended to work as a 'wrapper' for existing OPC Historical Data
Access Custom Interface Servers, providing an automation friendly mechanism to the functionality provided by the
The automation interface provides nearly all of the functionality of the required and optional Interfaces in the OPC
Historical Data Access Custom Interface. If the OPC Historical Data Access Custom server supports the interface, the
functions and properties at the automation level will work. Automation interfaces generally do not support optional
capabilities in the same way that the custom interface does. If the underlying custom interface omits some optional
functionality then the corresponding automation functions and properties will exhibit some reasonable default behavior
as described in more detail later in this document.
The interfaces are fully supported by VC++ and Visual Basic 5.0. They allow any application which has an OLE
Automation Interface (e.g. VB, VC++, and VBA enabled applications) to access the OPC Interface, according to the
limitations of the respective application.
The interface described in this specification specifically does NOT support VBScript or Java Script. A separate wrapper
could be developed to accommodate the needs of VBScript and Java Script. However such an effort is outside the scope
of this specification.