Answer: "PMIx" = "OpenPMIx". This is answered elsewhere in the documentation. https://docs.openpmix.org/en/latest/ says, "You will see OpenPMIx frequently referred to as just PMIx. While there is a separate PMIx Standard, there are (as of this writing) no alternative implementations of that Standard. In fact, the Standard post-dates the library by several years, and often lags behind the library in terms of new definitions. Thus, it is customary to refer to the library as just PMIx and drop the longer name - at least, until some other implementation arises (which many consider unlikely)." And https://docs.open-mpi.org/en/v5.0.x/installing-open-mpi/required-support-libraries.html says, 'While OpenPMIx is the formal name of the software that implements the PMIx standard, the term “PMIx” is used extensively throughout this documentation to refer to the OpenPMIx software package.'