In which DLL is the COM interface iStream defined?

I'm a complete newbie to Windows and COM programming, trying to use com4j in order to call a COM object from Java.

Com4j generates Java interfaces from COM definitions "often found in .ocx, .dll, .exe, and/or .tlb files" . It was easy for me to locate the .ocx file of my target COM object, but I have no clue regarding the standard interface iStream.

Microsoft's documentation mentions OLE32.DLL ( c:\Windows\Windows32\Ole32.dll ?) , but neither the com4j generator nor oleviewer succeed in opening this file.

Any hints?

It looks like it is defined in comsvcs.dll .