PIDINST identifier

[ACz-UniBi]

Dear, I'm wondering that PIDINST_Identifier is an identifier.

The whitepaper offers information on "The PIDINST PID is used to identify measuring instruments,...". Could you point me to the place of describing the PIDINST identifier?
PIDINST seems to me as an initiative for bringing up some issues in the context of Instruments, eg. visibility.

From 'Persistent Identification of Instruments':
"Between March 2018 and October 2019, the Research Data Alliance (RDA) Working Group (WG) Persistent Identification of Instruments (PIDINST) ..."

The PIDINST_id as a datatype isn't a (data)type like DOI_id is.