That looks beautiful. So the hash basically says "I trust this source"? >>The important thing in both cases would be to allow shared caching between sites with

That looks beautiful. So the hash basically says "I trust this source"? >>The important thing in both cases would be to allow shared caching between sites without forcing everybody to agree on which CDN is the most pleasing. Notice that the cannonical-uri is only a name, it is not supposed to be dereferenced. Yes, you put it much better than I could have. Thank you!