ePublisher does not recognize system DTD
When given a local DTD file, ePublisher will not recognize the DTD and throw an error saying that there is an unknown protocol. This will even happen using language such as file:\\
The URL you are specifying: "C:/automap/DITA-OT/dtd/example.dtd" is not acceptable to the DITA-OT Java run-time. ePublisher leverages the DITA-OT for early stage processing and therefore makes use of the Java run-time.
So, the trick is to find a SYSTEM URL that Java likes.
The "file:" sets the appropriate protocol for the URL which should then allow the Java run-time to correctly interpret the Windows file path.