Of course there can be. Alphabetic ordering would work. Yes, it might be wrong, but it would work as a fallback in the absence of any other information.
If PEP 825 chooses to say that lack of any explicit ordering is an error, then that should be stated explicitly in the PEP (if for no other reason than because the reader could otherwise assume that there is a default ordering[1]).
What I’m trying to do is explain my difficulty in understanding the PEP’s handling of ordering data as it stands. I’m clearly not managing to do so. I don’t think there’s a lot of point in continuing to debate the issue, we’re simply both going to get more frustrated.
If you don’t want to go with my suggested model of having ordering data be index-level rather than wheel-level, that’s your choice as PEP authors.
I would recommend that you review how the PEP presents this area and try to make it more understandable. At the end of the day, I need to approve or reject this PEP, and “is it clear and well-defined” is a key factor in that decision. I won’t let my difficulty understanding things be the sole deciding factor (it’s a complex area and I’m definitely not an expert) but there’s not been much evidence in the DPO discussions[2] to suggest that everyone else understands the details and it’s only me that’s struggling. Admittedly, there’s little evidence the other way around either. It would be helpful if there were more participation in this discussion… 