Side question about "Structured additional information" StrdBkgInf

[sdespont]

I know that this question is a bit out of scope of this library, sorry about that, but is there someone knowing which norm is defining StrdBkgInf string starting by "//U1" ? It seems the same syntax that SWICO have defined, except the staring string.

SWICO has defined a syntax definition, but the string must start by //S1 https://www.swico.ch/media/filer_public/20/76/2076a19a-a017-438a-bc9a-73b1a5980d00/v2_qr-bill-s1-syntax-de.pdf / https://www.swico.ch/media/filer_public/1c/cd/1ccd7062-fc69-40f8-be3f-2a3ba9048c5f/v2_qr-bill-s1-syntax-fr.pdf like

So, if there is someone with a reference about "U1" standard, it would be very useful.