I have changed the subject line in order to focus on the issue of intervals and the objection to the slash character.
Simon Grant said:
"I do think we need an alternative to ISO for a range. In particular, I think we need external delimiters -- some sort of brackets -- enclosing the range. This could go with the ... syntax as an alternative to ISO "/". I don't currently have any positive suggestions for how to represent "one value from this range" except that it should use exactly the same syntax as the range."
Again I want to be sure that we are properly distinguishing ranges from intervals. I often find myself saying "range" when I mean "interval" so I do know how easy a mistake it is to make, and I am going to assume that Simon means "interval" here. In any case, ranges ARE externally bracketed.
Anyway, I have been intending to get back to this issue. I am reasonably persuaded by this and earlier discussion that there is sufficent concern about the use of "/", even though it is part of ISO 8601, that we need to investigate alternatives.
I haven't thought this all through but would like to suggest this approach: I propose that for a "standard" interval, EDTF prescribe the 8601 approach. For a non-standard (non 8601 conforming) interval we deviate from 8601 and use an alternative syntax that is acceptable to everyone. Does this seems like a reasonable approach?