[uf-new] Separating File Content from File Format

Charles Iliya Krempeaux supercanadian at gmail.com
Fri Apr 6 12:03:32 PDT 2007

Hello Manu

On 4/6/07, Manu Sporny <msporny at digitalbazaar.com> wrote:
> Charles Iliya Krempeaux wrote:
> >> Hmm, reading that gives me the impression that parameters are defined
> >> when media types are registered, and aren't something we can add to
> >> suit our needs.
> >
> > I don't believe that is the case.
> >
> > I believe (according to the spec) you are free to create your own
> > Content Type parameters.
> I disagree, you could break backwards compatibility if you start tacking
> on parameters that are not defined in the MIME-type (which is used in
> the Accept and Content-Type fields):
> "When sending data to older HTTP applications, implementations SHOULD
> only use media type parameters when they are required by that
> type/subtype definition."[1]
> I can't find any statement in the literature that says that you can add
> parameters that are not in the "Required" or "Optional" listing.
> Furthermore, RFC 2045 states:
> "Use of non-registered media types is discouraged." [1]
> "MIME implementations must ignore any parameters whose names they do not
> recognize."[2]
> I believe this means that web browsers should ignore any parameters
> whose names they do not recognize. That means if it isn't in the
> MIME-Type specification, it should be ignored by any implementation
> reading a field containing the MIME-Type.
> In short - if it isn't registered with the Mime-Type - you shouldn't be
> using it.
> -- manu
> [1] http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.7
> [2] http://rfc.net/rfc2045.html#p10

I don't think we are disagreeing.

You are saying that it says we SHOULD NOT use them.  And I'm not arguing that.

But "SHOULD NOT" is NOT the same a "MUST NOT".

And therefore, despite the encouragement (from the spec) to NOT make
up your own Content Type parameters, you still could.  And if you did,
you would still be complying with the spec.

    Charles Iliya Krempeaux, B.Sc.

    charles @ reptile.ca
    supercanadian @ gmail.com

    developer weblog: http://ChangeLog.ca/

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