Am 22.09.2020 um 16:06 schrieb Denis Maier :

Hi, I need to produce PDF/a. I've followed the advice on the Wiki, and the file validates with: https://www.pdf-online.com/osa/validate.aspx But Acrobat complains about some problem with the XMP definition. Does anyone know more about this?

Different validators have different opinions on valid PDF/A. :-/ But that might be the state of 2017 when Luigi(? or was it Giuseppe?) presented his work on PDF/A... Did you try veraPDF? https://openpreservation.org/products/verapdf/ Hraban