Comments are more than welcome.
This proposal is intended primarily to establish a format for the metadata and secondarily to determine what other pieces are required to make an URC resolution service work. The resolution service needs to parse the complete URC set, or consult a preparsed table, to return the appropriate info. This set has a bit more info than is strictly needed. The content model of URC is arranged simply for convenience in the present trial, and should be regarded pretty much as a placeholder or strawman. Practically everything is open, but here's a short list.