Notes on PATCH

Characterizing the difference between the two approaches to Content-Type:

1. the current approach described in <http://www.ietf.org/internet-drafts/draft-dusseault-http-patch-05.txt> is that the PATCH method's Content-Type header is modelled as saying "this is what the content type of the request body is". Thus, it doesn't matter if the PATCH request is modifying a resource of type text/plain or an image/gif or something else, the content-Type header contains the MIME type of the request body.
2. The approach proposed by Mogul, similar to the approach taken in <http://www.ietf.org/rfc/rfc3230.txt>, is that the Content-Type header should refer to the content type of the resource being addressed, and that diff or compression algorithms that happen to be used can be specified in the IM header.

The difference between Content-Type applying to the message body, and Content-Type applying to the resource, is in my mind a matter of HTTP design theory. Either approach can be made to work as a practical matter (at least in the absence of content negotiation). The former approach seems more natural to me because Content-Length and Content-Encoding both clearly apply to the message body, so I had always assumed that Content-Type does as well.

-- LisaDusseault - 27 Sep 2004