RDF error

Got a problem popping up in different parts of my Agridrupal install:

Notice: Constant RDF_ARC2_PATH already defined in include_once() (line 13 of /***/sites/all/modules/rdfx/rdfx.module).

Likely the following faulty view result is related to this?

[node:field-ag-lastname], [node:field-ag-name]

Any hints on resolving this error message?