Primary corresponding authors are often identified in submission and production systems, and that info is used for many purposes, including read & publish deal billing, proof delivery, etc. In the final version of an article, if multiple authors are tagged for correspondence using @corresp="yes" it becomes impossible to identify the *primary* corresponding author. As read & publish deal eligibility based on the primary corresponding author's affiliation grows in use, reporting via JATS on platforms like the OA Switchboard becomes increasingly inaccurate. Same goes for JATS XML ingested by Dimensions, CHORUS, etc. So it's becoming increasingly important to distinguish the primary CA.
On the JATS listserve, Nikos suggested tagging: . Of course, it would be very helpful for such tagging to be somewhat of a standard practice so that any organization using the XML knows what to look for. Perhaps this can be incorporated into the JATS4R Authors and affiliations recommendation.