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Re: Comments on the HTTP/1.0 draft.

From: Roy T. Fielding <fielding@avron.ICS.UCI.EDU>
Date: Fri, 09 Dec 1994 18:03:40 -0800
To: Marc VanHeyningen <mvanheyn@cs.indiana.edu>
Cc: http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com
Message-Id: <9412091803.aa17593@paris.ics.uci.edu>
Marc VanHeyningen writes:

> Kindly show me where the MIME RFC requires conforming implementations to
> check the registry; I can't seem to find it in my copy.

RFC 1521, Section 4:

     content  :=   "Content-Type"  ":"  type  "/"  subtype  *(";"
     parameter)
               ; case-insensitive matching of type and subtype

     type :=          "application"     / "audio"
               / "image"           / "message"
               / "multipart"  / "text"
               / "video"           / extension-token
               ; All values case-insensitive

     extension-token :=  x-token / iana-token

     iana-token := <a publicly-defined extension token,
               registered with IANA, as specified in
               appendix E>

     x-token := <The two characters "X-" or "x-" followed, with
                 no intervening white space, by any token>

A BNF defines how a conforming application should *parse* the input.
RFC 1521 specifies that the parser should declare a syntax error if the
MIME type is not registered with IANA.  RFC 1590 only changed the registration
procedure -- it did not change the MIME requirements.  Naturally, no mail
application I know of is stupid enough to implement this requirement --
they generally just check the ~/.mailcap for any token/token types.

HTTP doesn't care what the actual content-type is of the object-body.
All it cares about is that the Content-Type header can be parsed, and thus
it gives the only valid parsing rule possible for HTTP.

> The HTTP spec should, at bare minimum, mention these issues and encourage
> registration of types that are employed.

It already mentions these issues and includes explicit reference to how
media types are registered.  I will attempt to elaborate on the finer details,
but the decision HAS been made that HTTP is not a MIME-conformant application.


......Roy Fielding   ICS Grad Student, University of California, Irvine  USA
                                     <fielding@ics.uci.edu>
                     <URL:http://www.ics.uci.edu/dir/grad/Software/fielding>
Received on Friday, 9 December 1994 18:19:47 EST

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