[HDR-photo] XMP sidecar file for HDR images - Does it make sense?

[Geraldine Joffre]

A sidecar XMP file for an HDR image could store the following type of information:
- Filename and path of the source images used to produce the HDR image
- Exposures of the source images
- Relevant exif data hat did not change between the exposures (focal length,
camera model, owner, ...)
- Color primaries and white point (or name of the color profile of the source
images)

The advantage of such XMP file is that the metadata of the HDR image would be
stored in a standardized way, easily accessible by other applications -even
directly readable by users-, whereas the various HDR formats that exist have
all their own way to store metadata, and do not always include
photography-related tags anyway.

The drawback I am seeing though is the potential confusion with XMP files that
store the settings used to tone map HDR images. If an HDR image has an XMP
file containing metadata type of information as proposed above, should the
settings used to tone map this HDR image be stored in a separate XMP file? If
so, how to differentiate both files to avoid confusion? And wouldn't the
terminology "sidecar file" loose its sense if they are two of them associated
with the same HDR image? 

If not, i.e. if both the HDR image metadata and the tone mapping setting are
included in a single XMP file, could it be confusing to have one part of the
information that relates to the original HDR image (and does not change) and
the other part to the processing? And how to differentiate between an XMP file
that contains both type of information and one that contains only tone mapping
settings?

Any comment/input/suggestion will be appreciated.

Thanks,

Geraldine