I attended PDF Week 2023 a few weeks ago. One of the discussions in the PDF/UA liaison working group meeting (PDF/UA LWG) was on a work-in-progress spreadsheet(direct Excel doc link) that cross-referenced a lot of the concepts in Core-AAM and HTML-AAM.

I suggested it may be appropriate to work together so that the mappings would not be duplicated in multiple documents. The Excel doc could be converted to an AAM doc (leveraging a lot of the shared spec editing tools like ReSpec) and cross-referencing Core-AAM or HTML-AAM mappings, instead of duplicating them. While I did not agree to be a primary editor, I did offer to help @PaulRayius get it set up and running, if he and other responsible parties think it's a good path forward.

I do not know about the copyright, intellectual property, or other legal implications of a joint deliverable between W3C and PDFA. Counsel on both sides should consider that and probably develop a memorandum of understanding (MoU) or some other contractual agreement. FYI @DuffJohnson and @michael-n-cooper