In fact as we use ISO dates order is directly related to string order
I would suggest that if MIN() and MAX() can be used with Strings in real world SQL implementations, then it’s ok for us (although weird for me!); but if not, I wouldn’t do it.
Funny thing is that most SQL implementations support min and max over strings (maybe just an alias of 'Select stringvalue from table order by stringvalue ASC|DESC limit 1')
In XQuery, min and max functions can be applied over any atomic type, i.e number types dates, times, string and even boolean
Typo in multiple places: “Integer of Real”; you meant “Integer or Real”.
In fact, the RM model has a notion of ordered objects - every DV_ORDERED for example. But I guess it’s ok not to support that here.