The open method has open and open return parameters:
Open(fileName, openParams, openReturnParams)
How do you identify the actual constants for each type of parameter and the definitions for those constants?
The Extendscript documentation is atrocious. All they did is create a constants chapter that merely lists all the constants for all methods but does NOT define what the constants do NOR tell you what method or methods the constants are for. Its absolutely maddening.
That said you are right about the FDK documentation. This actually tells you what the parameters for the open method are and defines them.