I'm trying to integrate with Adobe InDesign and a plugin the is already created. Where do Instance and Document Id's come from? Are they meaningful or just a place holder to identify a file?
Are you talking about the Document IDs from the Media Management Schema (xmpMM:DocumentID)? If so, those are generated by the CS apps, usually on Save/Save As.. commands, and are designed really to be used by DAM systems.
See the XMP Specifcation on Page 43. It discusses the MM Schema.
Hope that helps.
Europe, Middle East and Africa