The requirement DMS-REQ-0030 only applies to PVIs. Similarly, the requirement DMS-REQ-0328,
The persisted format for Processed Visit Images shall be fully documented, and shall include a description of all image characterization data products.
also only applies to PVIs.
I think some refactoring is in order. We should introduce a requirement to report a WCS for difference images (presumably the same one from the PVI), and another to determine a WCS for all coadded images (I don't believe we have such a requirement now), and we should exclude from both these new requirements and from DMS-REQ-0030 any discussion of persistence. We should then add a requirement subtree something like this, rooted in section 1.1, "General Considerations" for "Data Products" in the DMSR:
1.1.8 "Image Data Persistence"
The DMS shall make all image data products available to end users, upon request, in the FITS 4.0 file format.
184.108.40.206 "Persisted Image Format Documentation"
The persisted format for all image data products released to end users shall be fully documented, including a description of all image characterization data products.
220.127.116.11 "FITS-compatible WCS persistence"
The DMS shall include a browse-quality approximate WCS in every FITS image file provided to end users, using WCS representation methods from the FITS 4.0 standard.
Discussion: This ensures that all commonly-available FITS-viewing tools can at least approximately indicate the coordinate system in a display.
18.104.22.168 "Precise WCS persistence"
The DMS shall include the full computed WCS for all calibrated images released to end users in (... language Tim Jenness can help us craft about using a community-readable format ...)