[michaelcgorman]

Another idea could be to include the separator character as part of the attribute (e.g. zone="profile:" or zonechar=":"). I'm not a huge fan of imposing mandatory URL structure, either, but I chose the colon since it is already valid and it's relatively pretty. (/profile:michaelcgorman looks nicer than /profile.php?id=michaelcgorman, at least to me)

Edit: I think I remember seeing something diff-like when working on a custom CalDAV feed a couple of years ago. Though that may have been CalDAV-specific, like a date-range.