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Re: PATCH thoughts...

From: Alex Rousskov <rousskov@measurement-factory.com>
Date: Fri, 30 Apr 2004 15:55:41 -0600 (MDT)
To: Lisa Dusseault <lisa@osafoundation.org>
Cc: HTTP working group <ietf-http-wg@w3.org>
Message-ID: <Pine.BSF.4.58.0404301536120.3309@measurement-factory.com>


On Fri, 30 Apr 2004, Lisa Dusseault wrote:

> RFC2616, section 7.2.1 only requires Content-Type for entity bodies,
> not for other non-entity request bodies:
>
>     When an entity-body is included with a message, the data type of that
>     body is determined via the header fields Content-Type and Content-
>     Encoding.

The above is not really a requirement. Content-Type is not a REQUIRED
header. Content-Encoding is only needed for encoded content. The
presence and transfer-length of request body is determined according
to these rules (see Section 4.4 for details, subject to errata):

   2.If a Transfer-Encoding header field (section 14.41) is present
     ... then the transfer-length is
     defined by use of the "chunked" transfer-coding (section 3.6)

   3.If a Content-Length header field (section 14.13) is present, its
     decimal value in OCTETs represents both the entity-length and the
     transfer-length.

   The presence of a message-body in a request is signaled by the
   inclusion of a Content-Length or Transfer-Encoding header field in
   the request's message-headers. A message-body MUST NOT be included in
   a request if the specification of the request method (section 5.1.1)
   does not allow sending an entity-body in requests. A server SHOULD
   read and forward a message-body on any request; if the request method
   does not include defined semantics for an entity-body, then the
   message-body SHOULD be ignored when handling the request.

There are other related MUSTs.

> WebDAV seems to have interpreted this requirement more broadly, as
> if it were worded "When a body is included with a message, ..." For
> example, PROPFIND requests contain a body that is not an entity
> body, but instead additional command detail.

IMO, any body is "entity body" from HTTP point of view. There are just
different entities being embodied.

> One compromise is to include Content-Type with a reasonably
> appropriate MIME type, but one that doesn't need to specify the diff
> format used.
>
>        PATCH /file.txt HTTP/1.1
>        Host: foo
>        If-Match: "def"
>        Content-encoding: gzip
>        IM: gdiff
>        Content-Type: application/octet-stream

As far as I can see, the above request will not be handled correctly
by intermediaries (they will drop its body). You need either
Content-Length or Transfer-Encoding header.

HTH,

Alex.
Received on Friday, 30 April 2004 17:55:44 GMT

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