How do I associate Oasis DTD to my exported topics?

I exported a number of files that are associated with our bookmap.  However, when I open a file (such as the bookmap) I get a number of validation errors stating that the @ish* attributes cannot be validated.

To fix this I had Oxygen use the bookmap.dtd file that is located in my ./username/AppData/local/SDL/ folder, but the errors persist.

C:\Users\myname\AppData\Local\SDL\InfoShare Client\0759605102\Config\DocTypes\dita-oasis\1.2\bookmap\dtd\bookmap.dtd

Is there any solution to this issue?  I'd really like to use these files for some OT plugin development work.