Failed to open OPPID SS6 schema

Hello All,

I'm using OPPID SS6, the workspace(schema) is modified by someone else. When I tried to open OpenPlant_PID.01.07.ecschema.xml with class editor(all schema xml files are exported from PW), and located the missing schema files, then it failed, the reason is "the class 'PIPING_SPECIAL' requires class 'PIPING_SPECIAL'". The workspace seems work fine(I didn't tough piping_special yet), I'd like to know, how to open it. Thanks a lot.