Ignore:
Timestamp:
Jan 13, 2013, 2:22:41 AM (7 years ago)
Author:
fielding@…
Message:

Accept-Language: clean up prose and note descending order of priority for equal weights (as defined in RFC4647 and original HTTP); partly addresses #426

File:
1 edited

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  • draft-ietf-httpbis/latest/p2-semantics.html

    r2118 r2119  
    19991999      </p>
    20002000      <div id="rfc.figure.u.33"></div><pre class="text">  Accept-Language: da, en-gb;q=0.8, en;q=0.7
    2001 </pre><p id="rfc.section.5.3.5.p.5">would mean: "I prefer Danish, but will accept British English and other types of English". (See also <a href="http://tools.ietf.org/html/rfc4647#section-2.3">Section 2.3</a> of <a href="#RFC4647" id="rfc.xref.RFC4647.2"><cite title="Matching of Language Tags">[RFC4647]</cite></a>)
    2002       </p>
    2003       <p id="rfc.section.5.3.5.p.6">For matching, <a href="http://tools.ietf.org/html/rfc4647#section-3">Section 3</a> of <a href="#RFC4647" id="rfc.xref.RFC4647.3"><cite title="Matching of Language Tags">[RFC4647]</cite></a> defines several matching schemes. Implementations can offer the most appropriate matching scheme for their requirements.
    2004       </p>
    2005       <div class="note" id="rfc.section.5.3.5.p.7">
    2006          <p> <b>Note:</b> The "Basic Filtering" scheme (<a href="#RFC4647" id="rfc.xref.RFC4647.4"><cite title="Matching of Language Tags">[RFC4647]</cite></a>, <a href="http://tools.ietf.org/html/rfc4647#section-3.3.1">Section 3.3.1</a>) is identical to the matching scheme that was previously defined in <a href="http://tools.ietf.org/html/rfc2616#section-14.4">Section 14.4</a> of <a href="#RFC2616" id="rfc.xref.RFC2616.1"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2616]</cite></a>.
    2007          </p>
    2008       </div>
    2009       <p id="rfc.section.5.3.5.p.8">It might be contrary to the privacy expectations of the user to send an Accept-Language header field with the complete linguistic
     2001</pre><p id="rfc.section.5.3.5.p.5">would mean: "I prefer Danish, but will accept British English and other types of English". If no quality values are assigned
     2002         or multiple language tags have been assigned the same quality, the same-weighted languages are listed in descending order
     2003         of priority. Additional discussion of language priority lists can be found in <a href="http://tools.ietf.org/html/rfc4647#section-2.3">Section 2.3</a> of <a href="#RFC4647" id="rfc.xref.RFC4647.2"><cite title="Matching of Language Tags">[RFC4647]</cite></a>.
     2004      </p>
     2005      <p id="rfc.section.5.3.5.p.6">For matching, <a href="http://tools.ietf.org/html/rfc4647#section-3">Section 3</a> of <a href="#RFC4647" id="rfc.xref.RFC4647.3"><cite title="Matching of Language Tags">[RFC4647]</cite></a> defines several matching schemes. Implementations can offer the most appropriate matching scheme for their requirements. The
     2006         "Basic Filtering" scheme (<a href="#RFC4647" id="rfc.xref.RFC4647.4"><cite title="Matching of Language Tags">[RFC4647]</cite></a>, <a href="http://tools.ietf.org/html/rfc4647#section-3.3.1">Section 3.3.1</a>) is identical to the matching scheme that was previously defined for HTTP in <a href="http://tools.ietf.org/html/rfc2616#section-14.4">Section 14.4</a> of <a href="#RFC2616" id="rfc.xref.RFC2616.1"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2616]</cite></a>.
     2007      </p>
     2008      <p id="rfc.section.5.3.5.p.7">It might be contrary to the privacy expectations of the user to send an Accept-Language header field with the complete linguistic
    20102009         preferences of the user in every request (<a href="#fingerprinting" title="Browser Fingerprinting">Section&nbsp;9.6</a>).
    20112010      </p>
    2012       <p id="rfc.section.5.3.5.p.9">As intelligibility is highly dependent on the individual user, it is recommended that client applications make the choice
    2013          of linguistic preference available to the user. If the choice is not made available, then the Accept-Language header field <em class="bcp14">MUST NOT</em> be given in the request.
    2014       </p>
    2015       <div class="note" id="rfc.section.5.3.5.p.10">
    2016          <p> <b>Note:</b> When making the choice of linguistic preference available to the user, we remind implementers of the fact that users are not
    2017             familiar with the details of language matching as described above, and ought to be provided appropriate guidance. As an example,
    2018             users might assume that on selecting "en-gb", they will be served any kind of English document if British English is not available.
    2019             A user agent might suggest in such a case to add "en" to get the best matching behavior.
     2011      <p id="rfc.section.5.3.5.p.8">Since intelligibility is highly dependent on the individual user, user agents need to allow user control over the linguistic
     2012         preference. A user agent that does not provide such control to the user <em class="bcp14">MUST NOT</em> send an Accept-Language header field.
     2013      </p>
     2014      <div class="note" id="rfc.section.5.3.5.p.9">
     2015         <p> <b>Note:</b> User agents ought to provide guidance to users when setting a preference, since users are rarely familiar with the details
     2016            of language matching as described above. For example, users might assume that on selecting "en-gb", they will be served any
     2017            kind of English document if British English is not available. A user agent might suggest, in such a case, to add "en" to the
     2018            list for better matching behavior.
    20202019         </p>
    20212020      </div>
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