The OPC specifications define component interfaces based on the Microsoft (D)COM technology. (D)COM still is an important part of all Windows operating system versions. Native Windows applications need COM for inter-process communication.
COM was created in 1995 to replace OLE. Distributed COM (DCOM) was added in 1997 as an extension to COM to allow network-based component interaction. Because of DCOM’s roots in older binary and component-based protocols, it fails to deliver the flexibility needed in today's networked environments, is problematic with Firewalls and is cumbersome to deploy and maintain. In 2002 Microsoft introduced .NET with Web Services and .NET Remoting as the base for distributed applications. .NET Remoting provides inter-process communication features and Web services provide interoperability, loosely coupled programming models, and communication based on standards-based protocols such as XML, WSDL, SOAP. The OPC Foundation created the XML DA specification for OPC Data Access applications based on the Web Service technology. .NET3 combines Remoting and Web Services into the Windows Communication Foundation and implements additional web services standards such as WS-Security. Despite these developments still most OPC applications are built on the DCOM based OPC DA specification.