Specify which URL formats are acceptable within $batch, and which to prefer

Being able to specify a url that is relative to the $batch seems like a nice feature; I could (in theory) have the same $batch request applied to two different services that had the same schema (don't know how common this would be in practice, though). I think servers should support all three, with c) taking precedence over (b) which takes precedence over (a). Accepted: https://www.oasis-open.org/apps/org/workgroup/odata/download.php/47172/latest/odata_meeting-11_on-20121011-minutes.html