Below I have inserted a table which shows how The PDF Info Dictionary tags and specific XMP tags are related and how they can be translated.
Thus, in your GUI, I assume you would create the PDF Info dictionary Fields (Title, Author, Subject, Keywords, Creator, Producer, creation date, modification date) for the user to fill-in and then the corresponding XMP tags (as shown in the above inline table) would be updated at the same time (as you said, enabling a check box would allow a user to also update XMP tags when they entered data in the info dictionary fields).
1. how deletion of tags would be implemented (possibly overwriting with new entries)?
2. how duplication of tags would be handled/avoided (possibly by overwriting all tags present)
We look forward to learning about your progress regarding the above development. I also look forward to promoting and recommending your app when this above piece is complete.
Thank you kindly.
See uploaded image: XMP_Metadata_with_Corresponding_PDF_Info_Dict_Metadata.jpg