Standards or widespread guidelines for updating of Exif or other metadata when modifying photos or other images?

Question

I'm working on software that allows users to upload photos (or, potentially, any image). The photos are scaled to a maximum size (to save space) and as part of that change to the image I want to copy the Exif metadata from the original image to the resized image. If I do so however at least some of the metadata will no longer reflect the resized image (e.g. dimensions). Should I also update that metadata or should I simply preserve the original data?

Are there any standards or guidelines with regard to what metadata should be modified when editing an image; what should not be modified?

For my particular circumstances, the original image will not be retained by my software (tho it may or may not by the creator).

Answer 1

Broad answer is to use Metadata Working Group guidelines (PDF). Specifically, yes, the metadata should include the new image size, as well as the Modification Date/Time.