Re: [Technical Errata Reported] RFC7231 (6149)

"Roy T. Fielding" <fielding@gbiv.com> Wed, 29 April 2020 17:29 UTC

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From: "Roy T. Fielding" <fielding@gbiv.com>
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Date: Wed, 29 Apr 2020 10:26:18 -0700
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Cc: Julian Reschke <julian.reschke@greenbytes.de>, superuser@gmail.com, barryleiba@computer.org, Mark Nottingham <mnot@mnot.net>, Tommy Pauly <tpauly@apple.com>, eggyal@gmail.com, ietf-http-wg@w3.org
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Subject: Re: [Technical Errata Reported] RFC7231 (6149)
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Reject. This is not an errata in RFC7231.

While it is theoretically possible for media types to no longer define a
given parameter, it is not possible for them to limit usage of parameters
in HTTP. This example is still fine.

Note that this example has already been updated in http-core's Accept

  https://httpwg.org/http-core/draft-ietf-httpbis-semantics-latest.html#header.accept <https://httpwg.org/http-core/draft-ietf-httpbis-semantics-latest.html#header.accept>

....Roy

  

> On Apr 29, 2020, at 4:06 AM, RFC Errata System <rfc-editor@rfc-editor.org> wrote:
> 
> The following errata report has been submitted for RFC7231,
> "Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content".
> 
> --------------------------------------
> You may review the report below and at:
> https://www.rfc-editor.org/errata/eid6149
> 
> --------------------------------------
> Type: Technical
> Reported by: Alan Egerton <eggyal@gmail.com>
> 
> Section: 5.3.2
> 
> Original Text
> -------------
> The media type quality factor associated with a given type is
> determined by finding the media range with the highest precedence
> that matches the type.  For example,
> 
>  Accept: text/*;q=0.3, text/html;q=0.7, text/html;level=1,
>          text/html;level=2;q=0.4, */*;q=0.5
> 
> would cause the following values to be associated:
> 
> +-------------------+---------------+
> | Media Type        | Quality Value |
> +-------------------+---------------+
> | text/html;level=1 | 1             |
> | text/html         | 0.7           |
> | text/plain        | 0.3           |
> | image/jpeg        | 0.5           |
> | text/html;level=2 | 0.4           |
> | text/html;level=3 | 0.7           |
> +-------------------+---------------+
> 
> Corrected Text
> --------------
> The media type quality factor associated with a given type is
> determined by finding the media range with the highest precedence
> that matches the type.  For example,
> 
>  Accept: text/*;q=0.3, text/plain;q=0.7, text/plain;format=flowed,
>          text/plain;format=fixed;q=0.4, */*;q=0.5
> 
> would cause the following values to be associated:
> 
> +--------------------------+---------------+
> | Media Type               | Quality Value |
> +--------------------------+---------------+
> | text/plain;format=flowed | 1             |
> | text/plain               | 0.7           |
> | text/html                | 0.3           |
> | image/jpeg               | 0.5           |
> | text/plain;format=fixed  | 0.4           |
> | text/plain;delsp=yes     | 0.7           |
> +--------------------------+---------------+
> 
> Notes
> -----
> The optional "level" parameter of media type text/html was removed by informational RFC 2854 (The 'text/html' Media Type), [section 2](https://tools.ietf.org/html/rfc2854#section-2) of which states:
> 
>> Note that [HTML20] included an optional "level" parameter; in
>> practice, this parameter was never used and has been removed from
>> this specification.
> 
> More formally, [the current IANA registration of the text/html media type](https://www.iana.org/assignments/media-types/text/html), which is taken directly from [section 16.1 of the HTML specification](https://html.spec.whatwg.org/multipage/iana.html#text/html), does not include a "level" parameter.
> 
> Whilst the example is non-normative, it has given rise to misleading information—e.g. in the [MDN Web Docs glossary definition of "quality values"](https://developer.mozilla.org/en-US/docs/Glossary/quality_values)lues), which states:
> 
>> Some syntax, like the one of Accept, allow additional specifiers
>> like text/html;level=1. These increase the specificity of the value.
>> Their use is extremely rare.
> 
> Instructions:
> -------------
> This erratum is currently posted as "Reported". If necessary, please
> use "Reply All" to discuss whether it should be verified or
> rejected. When a decision is reached, the verifying party  
> can log in to change the status and edit the report, if necessary. 
> 
> --------------------------------------
> RFC7231 (draft-ietf-httpbis-p2-semantics-26)
> --------------------------------------
> Title               : Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content
> Publication Date    : June 2014
> Author(s)           : R. Fielding, Ed., J. Reschke, Ed.
> Category            : PROPOSED STANDARD
> Source              : Hypertext Transfer Protocol Bis APP
> Area                : Applications
> Stream              : IETF
> Verifying Party     : IESG
>