Benjamin Carlyle proposes an alternative to RFC 3229 (HTTP Delta Encoding) (which I admit I wasn't aware of):
The two basic approaches here are a one-URL solution or an "n"-URL solution. rfc 3229 uses a one-URL approach, where different diffs are returned to different clients from the main resource URL. An "n"-URL solution would give a unique URL to each diff. Adding URLs seems to be the answer to most problems in the REST domain, so let's have a go at applying it to this one.
At first glance, this seems pretty slick and in line with appropriate hypermedia usage.